Does a sibling whose name was added to bank accounts when she had power of atty have to include these assets as part of the estate when executing the will?

If a person (of legal age?) is named on a bank account they have the right of survivorship to the account and are not included in probate regardless of their status of POA/Excecutor. When you are Power Of Attorney you are responsible for showing every transaction you made. In most cases, if the family agrees, and there are any expenses that the Power Of Attorney can't afford themselves they can take it out of the account, but should produce the sufficient receipts or paperwork in the final Estate. This is a protection that the Power Of Attorney did not take funds out for other uses than looking after the said Person being protected such as: mother/father/brother/sister/grandparents. Any Heir in the Will can demand to see all final bank statements. POA only allows the grantee to use the funds/assets of the grantor on the grantor's behalf. As noted, the POA holder can, in some U.S. states, be reimbursed for reasonable expenses incurred while acting on the grantor's behalf. A POA DOES NOT give the grantee the right to do whatever they so choose with the assets of the grantor regardless of their being placed on bank accounts. A POA becomes null and void upon the death of the grantor, and ALL assets are turned over to the executor/executrix that is named in the will or if the person dies intestate the excutor/executrix appointed by the probate court.