My sister and husband are homeless/jobless again, my mother is 94 y/o, is HOH, and was insane with grief. My sister made herself and her daughter DPOA and added her daughters name as co-executor with me on my mothers will. My mother finally told me what happened as she is able to think clearer now and wants to know how my sister got away with this and why her bank or lawyer didn't make sure she knew what she was signing.
As already stated, your mom can make changes as often as she wants, but perhaps it would be good that she gets legal and financial advice from a disinterested third party.
But it won't be hard to fix things, now that mother is her competent self again.