What would happen if my 91 year old mother gets someone to take her out of the ALF and close the bank account that pays for the ALF?

Does someone have Power Of Attorney? Is she competent mentally? You many need to see an elder attorney, plus talk to her doctor if this is something your are worried about. If she has legal control over her money and does this with full consent, you could have a hard time preventing it. An attoney could advise you.
Good luck,
Carol