Legal Question in Wills and Trusts in Arizona

If she is on the account, then she has legal title to the money as well. Also, if the power of attorney is written correctly, that is added protection for your sister.

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If the account is titled in the name of both mother and sister, then she would be a joint owner of the account. If the account is titled in mother's name alone, then sister is an authorized signer and could write a check to herself. However, if sister is acting under the authority of mother's power of attorney (healthcare? general?) (Durable?), then your sister owes a fiduciary duty to mother and cannot take her money for herself, and must only use mom's money for mom's benefit.