Limited debit card for mil?

My mil (aged 91) is compos mentis in general but becoming forgetful. She has an inappropriate amount of money in her current account and has a debit card which she only uses to get cash out for day to day spending (with help from the local branch cashier). Now her local branch has closed and many shops are going cashless. She doesn’t like to take her card out shopping in case her purse is pinched. It’s happened before. So I wondered if I could open a new bank account in my name, transfer money into it from her account using my POA and give her a “carers card” with limited spend to use when out shopping. (The reverse of the usual carers card arrangement.) So if it is pinched the thief only has access to this account, not her overfull current account. She won’t move the excess from her own account as she is expecting huge bills for work on her flat over the next few months.
I’m looking at a Starling bank current account with a “companion card” for her and topping it up regularly from her main bank account.
Is this a good idea and can anyone suggest any other ways of giving her cashless shopping while safeguarding her bank account?

If you have POA, you have access to all her accounts in any case. I’d suggest leaving her current card with her, but opening a separate savings account in her name, which she doesn’t have a card for. Then all her pension goes into the savings account, and then a weekly Direct Debit into her card account. Works well for my son with learning difficulties.

Thankyou for the suggestion but the whole point is that she will not move all that money out of her current account and at the same time needs a card for shopping which , if stolen, will not let the thief spend too much especially now that the tap&go limit is soon going up to £100 per transaction. Also for the odd cash withdrawal which she will now have to do via the post office where there are some distinctly dodgy people hanging around.

You have POA.
These are your decisions to make now.
Don’t ask mum, she lacks capacity.
Do what needs to be done, and then tell mum what you have done to keep her safe.
That is why she gave you POA when she was well.