To answer your question, the guardian is under a fiduciary duty to act appropriately for the benefit of the ward. Whether or not that duty is breached by the conduct above is a factual determination.
Seems to me that you should consult with a plaintiff's attorney specializing in Elder Abuse.
This comment is general advice only. No attorney-client relationship is formed or intended, and an actual lawyer is necessary to examine the specifics of any situation to provide a complete answer.
As my colleague said, when someone is a guardian, he has certain requirements in terms of his behavior towards the person he is supposed to be helping. I would contact a lawyer who handles elder law and/or estate law, spend a little money for an hour of his or her time, and get an opinion.
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