How to stop niece from taking mom's money?

I observed my 95 year old housebound aunt respond to a call from her bank. She had a CD maturing and they asked her what to do with it. She told them to cash it out and it in her bank account. They did it. Just saying it can happen.

If your niece is communicating with her by phone or digitally I'd do everything to block her or have your mom's calls forwarded to your phone. If you have actual proof that the money is going to the niece I would inform her (the next time she tries to contact your mom) that there is currently an open investigation because there's concern over theft and fraud of a vulnerable senior. You don't need to say it's her, but just the insinuation should be enough to cause her to (hopefully) rethink what she's been doing.

I agree with Isthisrealyreal about contacting authorities but I'm pretty sure you'd have to have some actual proof -- one type of which would be your mom's medical diagnosis of cognitive/memory impairment. I also agree with Isthisrealyreal that closing out an account with that much money sounds fishy -- where did the funds go? Were they transferred to another account? Surely since she lives with you she didn't drive to the bank to accept the cashier's check without you knowing? If your mom told you this story, I'd be suspect of it. You can create an online account for her (with her permission and in her presence) and you can look into her banking activity, or ask your mom to show you recent statements so you can help her "reconcile" her checkbook.

I would call the police and APS.

This is financial exploitation of a vulnerable senior.

How did she close an account over the phone? I would be contacting the banking commission to find out wth?