Can a POA get a credit card other than those in his own name

As a fiduciary my responsibility is to keep intermingling my own expenses with those of the person I am responsible for. However in practice this has not been done so far and this will need to change now that I am officially POA. In fact I've been paying her bills since her husband's passing with my own credit card, but this is not a satisfactory solution because I am also using my credit card for other purposes. What I'd prefer to do is use a separate credit card in order to meet my responsibility of not intermingling finances.

The question is, since she has no credit card of her own, can I get one on her behalf as POA, or do I have to use one in my own name, or is there such a thing as a POA credit card?