If your sister has power of attorney over your mother, she has been given legal authority to act on your mother’s behalf for whatever matters the document covers. She is called the agent; your mother is the principal. That authority is real, but it is not unlimited, and it does not take anything away from your mother. As long as your mother has mental capacity, she can still manage her own affairs, override your sister’s decisions, or revoke the document entirely. Your sister’s duties run to your mother, not to you, which shapes almost every question you are likely to have from here.
What Your Sister Is Actually Allowed to Do
Power of attorney comes in two main forms, and your sister may hold one or both. A financial power of attorney lets her handle money matters: paying bills, managing bank accounts, filing taxes, dealing with investments and insurance. A healthcare power of attorney lets her make medical decisions, such as consenting to treatment, choosing doctors, or arranging long-term care. These are separate documents with separate authority, and holding one does not automatically grant the other.
A financial power of attorney can be broad or narrow. A general one hands the agent wide authority over nearly all financial matters. A limited one restricts authority to specific tasks, such as selling a particular piece of real estate or managing one account. The label matters less than the document itself, which spells out exactly which powers your sister has. If you want to know what she can and cannot do, asking to see the paperwork is the right starting point, even though she is not required to show it to you.
If your sister holds a healthcare power of attorney, she qualifies as your mother’s “personal representative” under federal privacy law. Healthcare providers must generally give her the same access to your mother’s medical records that your mother would have, including mental health information in the main medical chart. A therapist’s personal session notes kept separately from the patient file are the exception; those are not shared, even with the patient.1U.S. Department of Health & Human Services. Does Having a Health Care Power of Attorney Allow Access to the Patient’s Medical and Mental Health Records Under HIPAA If a provider reasonably believes your mother has been or may be subjected to abuse or neglect by the agent, the provider can refuse to treat your sister as the personal representative.2U.S. Department of Health & Human Services. If Someone Has a Health Care Power of Attorney for an Individual, Can They Obtain Access to That Individual’s Medical Record
What Your Sister Cannot Do
Certain things fall outside any agent’s authority, no matter how broadly the document is written. Your sister cannot create, modify, or revoke your mother’s will. She cannot vote in elections on your mother’s behalf. And the entire power of attorney terminates the instant your mother dies, so any action your sister takes after that is legally void and can expose her to liability.
Some powers are treated as so sensitive that the Uniform Power of Attorney Act, adopted in some form by most states, calls them “hot powers” and requires the document to grant them in explicit terms. These include making gifts from your mother’s assets, creating or changing beneficiary designations, creating or amending trusts, and changing rights of survivorship. If the document does not expressly grant these powers, your sister cannot exercise them even under an otherwise general power of attorney. This is one of the most commonly misunderstood points.
Self-dealing is where families run into the most trouble. Your sister generally cannot transfer your mother’s money to herself, write herself checks from your mother’s accounts, or make gifts to herself unless the document expressly authorizes it. Even when gifting is authorized, the default limit under the Uniform Power of Attorney Act caps gifts at the annual federal gift tax exclusion amount per recipient (currently $19,000 per person in 2025, adjusted for inflation). Going beyond what the document authorizes can expose her to civil liability and criminal charges for theft or embezzlement.
The Duties Your Sister Owes Your Mother
Accepting the appointment made your sister a fiduciary, which is the highest standard of obligation the law imposes. She must act in your mother’s best interest on every decision, not in whatever is convenient or profitable for herself. She must avoid conflicts of interest. She must handle your mother’s affairs with the care a sensible person would use managing someone else’s property. She must keep reasonable records of all financial transactions, receipts, and disbursements. And to the extent she knows your mother’s estate plan, she should try to preserve it.
Serving as an agent is often unpaid. Under the general rule in most states, an agent is not entitled to compensation unless the power of attorney document specifically allows it. Your sister can seek reimbursement for reasonable out-of-pocket expenses such as filing fees, postage, or mileage for trips to the bank.
A drop in the value of your mother’s investments is not, by itself, proof that your sister breached her duties. Markets fluctuate, and an agent acting carefully is not a guarantor of returns. But moving money into risky ventures that benefit her own interests, or neglecting obvious financial obligations, is a different matter.
What Rights You Have as the Non-Agent Sibling
Here is the part that frustrates most people in your position: as a sibling who was not named as agent, you generally have no automatic legal right to see your mother’s financial records, investment statements, or even the power of attorney document itself. Your sister is not legally required to share information about your mother’s affairs with you. Her fiduciary duty runs to your mother.
If your sister holds only a financial power of attorney, she has no authority to control who visits your mother. Even with a healthcare power of attorney, she can restrict visitors only if the document gives her that authority and she genuinely believes a visit would harm your mother’s health. An agent managing finances cannot bar you from the house or the hospital room.
Your mother’s own capacity matters a great deal here. If she still has it, she can tell you herself what is going on, show you the document, add safeguards to it, change agents, or revoke the power of attorney outright. A written revocation, ideally notarized, with notice sent to your sister and to any banks and providers that have been relying on the document, is what makes a revocation stick. Until those third parties receive notice, they may continue honoring your sister’s authority in good faith.
If You Think Your Sister Is Mismanaging Things
Start by separating disagreement from misconduct. You and your sister may have genuinely different views about what is best for your mother, and the law gives the named agent broad discretion to make those calls. Selling the family home or changing investment strategies may upset you and still be within her authority. A court will step in when the agent violates fiduciary duties, not when a sibling would have made a different choice.
When communication has not completely broken down, mediation is usually the sensible first step. A neutral mediator can help the family work through specific decisions without the cost and hostility of a courtroom fight.
If mediation fails or the situation involves genuine abuse, you can go to court. You can petition for an accounting that compels your sister to document every transaction she has made on your mother’s behalf. You can petition to have the power of attorney revoked or to have a guardian appointed. The court may appoint a guardian ad litem, an independent person assigned to investigate and represent your mother’s interests during the proceedings. If the court finds misconduct, it can revoke the power of attorney, order your sister to restore misappropriated funds, and appoint a guardian to take over going forward. An agent who breaches fiduciary duties can be sued to restore every dollar of the principal’s property to where it would have been without the violation, plus attorney’s fees, and depending on the severity, criminal charges for fraud, theft, or embezzlement are also on the table.
You are not the only line of defense. Many states require banks and healthcare providers to report suspected financial exploitation of vulnerable adults. Unusual transaction patterns, large unexplained withdrawals, or sudden changes to account ownership can trigger reports to Adult Protective Services or law enforcement, independent of anything the family does. If you see those patterns and your sister will not account for them, that is grounds to contact Adult Protective Services directly.
If your mother no longer has the capacity to revoke the power of attorney herself, the court route is the only route. A guardianship or conservatorship petition asks a judge to intervene, and the judge can revoke the power of attorney after finding the agent is not acting in your mother’s best interest. That takes evidence of misconduct or incapacity, not a preference for a different arrangement.
When the Power of Attorney Ends
The authority terminates automatically and immediately when your mother dies. At that moment, your sister loses all power to access accounts, make financial decisions, or interact with institutions on your mother’s behalf. Authority over your mother’s affairs transfers to the executor or personal representative named in her will, or appointed by a court if there is no will. These two roles never overlap. If your sister is also named as executor, she gains that authority through probate, a separate legal process, not through the power of attorney.
Other events end the authority as well: your mother revoking the document, your sister resigning, your sister becoming incapacitated herself, or in many states, the filing of a divorce or legal separation action between agent and principal. If a successor agent is named in the document, that person steps in when the primary agent can no longer serve, with the same authority unless the document says otherwise. If co-agents were named and must act jointly, a disagreement between them can stall decisions and may itself require court intervention.
The short version of all this: your sister has real authority but real limits, your mother keeps her own authority as long as she has capacity, and your path if something is genuinely wrong runs through a court, not through demanding records your sister is not required to hand over.