Don't tell her she can't swim with you. Just explain that you don't think you would be able to perform lifeguard duties. Nobody is entitled to ask you for any heroics, but I don't know that she even has this in mind she may simply find it reassuring, psychologically, to know that you could use a phone and call for help if she were having distress.
Whether she can safely swim is a question for her doctor; she may have been told that not swimming would be worse for her health.
Diverting donations from their intended beneficiaries, if that's what happened, is stealing and stealing from the poor at that. Part of ethics is holding people accountable.
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