GaAtty
It really depends upon whether or not she is mentally competent. That seems to be questionable, because if she were, presumably she would have done something about your son's actions regarding her credit cards. She would also not be asking for your help. So my assumption is that she is not competent. Assuming that, then you cannot take over her affairs without asking a court for guardianship UNLESS she previously gave you a financial power of attorney. If there is any question at all of her competence now, then she cannot sign a VALID power of attorney at this time. In other words, she must be able to fully understand what she is doing in order to give you control of her affairs. However, that does not mean that you cannot help her with paying her bills, etc. You do not have to "take over" in order to help. I will say, however, that in my opinion, you have a conflict of interest situation about to arise. It is going to put you in an awkward situation to "help" your mom with her money and "run her affairs" and on the other hand, not go after your son to make him replace her money, especially when you know that he has done something illegal to deprive her of her money. If you take no action against him to recover your mom's money, then a court may not consider you to be a suitable guardian for your mom because of your conflict of interest. I will also tell you that in most states, a court will require you to obtain a bond in the amount of your mother's assets before you can be her guardian. I do not know if this is required in your state. You should check.