I have power of attorney for my mother. She thinks she is able to be in charge of her finances, but they're a mess. Any advice?

I would say if Moms finances are so messed up there is some decline. Your profile doesn't say anything about Dementia. I didn't have to activate my POA. When Mom couldn't do it anymore I took over. But she gave it up to me too.

You need to read the POA document first, because they aren’t all the same. Sometimes, they only become active if the POA donor becomes incompetent. Normally, they can’t over-ride the wishes of someone who is still competent, but provide an alternative signature/ decision maker (for example, my daughter gave me a POA when she was going overseas for a while). This means that you have either to convince your mother that she needs to hand over managing to you, or you have to get a decision made (eg by a doctor) that she is not competent. Otherwise, yes, she just chooses to blow the lot.

It might help if you can get her to an accountant or financial planner, and best if you have enough information to set out a reasonably clear summary of the mess she is in. It would be good if the professional you choose can provide a ‘worst case scenario’ of what might happen to her if she doesn’t hand over to you. She may well believe them even if she doesn’t believe you. You might then be able to move on to the ‘therapeutic fibs’ that many people recommend, along the lines of ‘the doctor says that you must….’. You may need to provide a brief explanation in advance so that the professional knows the basic situation.

Remember the advice that many people give, to keep any financial dealings with her quite separate from your own personal finances. Make sure that you provide no ammunition to a creditor to say that you have taken responsibility for her debts.

Good luck in a difficult situation.

Being named Power of Attorney gives you no immediate powers. It needs to be activated. Read the document and see how to activate the power of attorney. The language is usually on the last page near the signatures.
Once it is activated, you can exercise any of the powers listed in the document and hopefully that includes controlling her finances.

I hope your POA is durable. You just have to step in. I had the same situation. I just had to keep telling my mother about the financial mistakes she had made and what that was costing her needlessly. You may have to say it many times but once this situation reaches the point I believe you are at there is no rational alternative.