Since Mom made me POA my sister refuses to hand over my Mom's bank statements, bills, etc. What do I do?

Many banks have their own version of a POA document, so going in with Mom is important.

How is it that your sister knows about expensive repairs and calls you? Does she have more contact with Mother? Is she a hands-on caregiver?

I think that Maggie is right and that you just have to go ahead with your duties, working around Sis. But if Sis is doing caregiving or even if she lives closer and sees Mom more often, it is also important that you try to maintain at least a civil relationship with her.

As I understand from reading posts on the subject, banks don't always honor a POA, however, if you have your mother with you, it should go smoothly.

Maggie is right on!

First, the car key problem. Pay mom for the car and get the title put in your name. Call the appropriate dealership and find out what's necessary to get keys made. Perhaps they'll need the VIN number. If you need to drive it before you buy it, get the keys right away.

Bypass your sister and deal with the bank. Bring in your mom and the power of attorney. Change the address for statements and correspondence to your home and ask for statement copies for however many months you'd like. Or, better still, your mom's accounts are no doubt on line. Have the bank help you access them THAT way, and you'll have all the history there is. Close whatever accounts your sister has access to immediately -- assuming she has mom's check books and can access her money.

Be prepared to World War III.