Mother, 92 with dementia, talks to the scammers and won't let caregivers answer her phone. Advice?

Get her home/landline phone on a VOIP (voice over ip) service like Magic Jack or Ooma. Then use their controls to filter out most of the scammer and telemarketing calls. They have good automated controls for detecting those numbers and blocking them. You can also manually add problem numbers to a block list. Or, at the extreme end, set it to only send through calls from certain numbers you select. Very low cost for these services - you do have to have internet - and essentially free long distance calling. Keep your same phone number.

With cell phones, these sort of blocking apps also exist, easy to install and use.

If you have POA, contact all the credit reporting agencies and lock her credit. That will at least keep anyone from getting into her credit by stopping any attempts to open credit cards or bank accounts in her name.

Next, contact her bank in writing to let them know she is a vulnerable adult. I don't know that you can get any protections requiring two signatures for her checks since you don't live nearby, but talk to the branch manager about what you can do.

I'd also install a Ring doorbell that you can see when someone comes to the door, and a couple of security cameras on her front door and driveway.

Please, take her phone away and tell her it no longer works…