Not an easy situation to be in, and good for you and your mom for standing up for yourselves. Also, good luck.
I've been in the doghouse for being unable to drive a family member who doesn't drive. She's not unable to drive, she just won't learn. She keeps saying, "I should really get my license", but she's been saying that for eight years. The most notable example is when she called the house to ask if I could drive her to a doctor's appointment the next day. It had been the only appointment she was able to get. Fair enough, but I had to work that day, and I told her that I couldn't do it and why.
There was a pause, then she said, "Oh...I was hoping you could do it. I was sort of counting on you." in a disappointed, almost reproachful tone. I don't know if she ever got to her appointment or not, but they were very chilly towards me the next time we saw each other.