Third party access while waiting for power of attorney

[Scrabsqueak]

I am struggling with helping my elderly mother in law. I live a long way away from her, and she is housebound and has no family support.
i am sending her food shops every week, but as she is a heavy smoker this is becoming very expensive. I have applied, with her consent, for Power of Attorney which, but it apparently takes around 6 months, by which time I am going to be skint!
she has carers, but not ones which shop for her, and she was ripped off by one who used her card to get cigarettes and took money.
I can not work out what to do next, her bank do not seem able to help beyond setting up a card which I could use …if I lived by her.
Any advice or experience?

Thank you all, I really do think I was too immersed to see a solution. A direct debit/standing order will probably be the best interim solution. I can set that up with her next week when I visit. I will also try adding her card as a payment to my supermarket shop, and see which one works out.
I appreciate all the responses, it has helped clarify my thinking.