To revert to the original topic, I think the key is 'she never learned to drive.' For our generation, seventies and younger, that is a deliberate choice, and I would think this friend has enjoyed a lifetime of being ferried around by her husband, now that he is unable to do so she expects others to take his place. If this offends people who have chosen not to drive, so be it. My aunt learned to drive in her late fifties when my uncle was stricken with motor neurone disease, and negotiated the Manchester traffic to various hospital with aplomb.
I spent six months last year unable to drive through illness, and while I hated the loss of my independence I began to see the advantages of being driven from door to door, not having to find a parking space, negotiate busy traffic, and of course, the saving in petrol and car tax. I did make contributions for petrol, and am now able to reciprocate by giving lifts to all the kind people who helped me.
The unfavourable comparison with another friend, the insistence on shopping on the day of her choice, not yours, the objection to coffee in the cafe and a complete lack of any form of recompense, indicate a woman used to having her own way, with a steely determination to continue doing so.
The demands for help will increase, and it is significant that the children are not available for much help; the son tried to help her use online shopping, which she refused to learn; they have probably had a lifetime of this.
The only way to deal with her is to become unavailable for trips that you are not intending to make. ie to the supermarket and the Surgery. Suggest a taxi. Doubtless she will contrive to make you feel guilty, but I think you can ride that out.