As a general matter, assuming the bank had no authorization, there would be a valid claim to have all money returned and potential damages for elder abuse. But that is a broad generalization of the claim here.
Fraud cases, especially involving elderly individuals, need quick attention from skilled attorneys. There is really not enough information provided to say "yes" definitely or "no" that the bank has over-reached. But to ensure that your mother is protected, contact the state bar immediately and ask for names of pro bono agencies that assist people with elder law claims. Also, make sure you maintain all of the records, keep notes of all conversations with the banks, and immediately write down your recollection of all facts and happenings to date. These records will be crucial once you are able to speak with an attorney.
I wish you all the best in this matter and hope it works out.
Nothing in this message should be construed as legal advice nor should the questioner act upon any of the information provided here. The attorney strongly encourages the questioner to seek independent legal counsel before acting.