Am I a bad son or is my mother selfish and ungrateful?

My mother is slowly going blind. Over the past few years, I pay for every meal when we eat out, I buy the movie tickets and popcorn everytime....when we shop together, I add her items to my items and pay for it all together. Recently I have bought her 3 large flatscreen tvs for her house, a large entertainment center to put one on, a washer and dryer, a sofa set for her living room, expensive vaccum cleaner and other electronics for her home. She deposited a check of mine last year to give me the money, but only gave me part of it and the rest, $1500, got spent, but I let it go. I fixed her credit so she could get financed for a huge new house and get approved for department store credit to buy nice new appliances with it for her house. Last week I got her a bmw to finance for her as a new car b/c her credit is bad again. Yesterday I bought her artwork she liked from the store because she was out of money and wanted it and I wanted to do it. Today while we shopped at a dept store, she carelessly ran over my fractured foot with the cart and I cussed at her and called her a spaz and asked her if she was f*cking retarded in a store (reaction to extreme pain). She wouldn't let it go, said I embarrassed her. We had a fight and I no longer want her in my life at this point. When we fight, she tries to attack my insecurities and then acts like a victim like I'm some kind of abusive son that treats his mother badly. I ask her what about all the things I get for her and thoughtful things I do, and she says Im throwing it in her face and tells me to take everything back. Shes one of those people that just won't admit their wrong or apologize. That probably wouldn't even help at this point. I have become tired of my mother's ungratefulness and even though she is disabled and I feel sorry for her I have become tired of her selfish attitude. Does this make me a bad person/son or am I right and we should just go our seperate ways?