Sadly your friendship seems to be over. You have tried your best, but it appears that since you couldn't give her a lift, regardless of how unwell you were, you were of no use to her.
When my BIL suffered from various cancers and kidney failure, we were there most days over the years supporting him and his wife. They had a son in London, who rarely came to visit and would phone us, telling us what we should be doing.
Many late night and early phone calls to take SIL to the hospital, were done willingly. After his death she ditched us! I had been seriously ill in hospital and she never came to visit, she lives five minutes away!
We haven't seen her for months, the last time was because she needed my help with an IT issue.
I thought we were good friends, obviously not!
When BIL was well enough to go on holiday, she would find excuses. The day before they were due to travel to Spain, she lost her passport. Now he is dead, she has been travelling all over Europe and her son frequently flies up to Glasgow to visit.
We learned a hard lesson there. It makes you reluctant to help in the future, although it was done out of love for my BIL.
Make a decision to take a step back, I am sure you will feel better in the long run.