gracechild70, if you write to the credit card company please use the term "nursing home". The term "assisted living" and "nursing home" tend to be used as one of the same, but technically the facilities could be different depending on where you live.
Assisted Living here in my area are all self-pay, thus to the credit card company that means the card holder has funds to pay off a debt. Nursing Homes can be either self-pay, or paid for by Medicaid meaning one has very little in funds, not enough to pay outside debts. Thus, using "nursing home" could help in the process.
You can simply send in a copy of your POA, along with a letter instructing that the account be closed. I'd also recommend reiterating you are not personally responsible for the debt. You can let the company know she's in assisted living. It won't stop the billing or collection process, but as POA, you should have the necessary authority to close the account down. I've not had any issue handling it this way to date with the one family member I did this for. Others may have more to add, of course.
Assisted Living here in my area are all self-pay, thus to the credit card company that means the card holder has funds to pay off a debt. Nursing Homes can be either self-pay, or paid for by Medicaid meaning one has very little in funds, not enough to pay outside debts. Thus, using "nursing home" could help in the process.
Best wishes.