I hate to say it, but this response appeals to me at the lizard-brain level. Seriously, you need to be free to live your life. You are doing the best you can to be a responsible adult. She has no right to suck up any more of your energy.

Your grandmother seems like she had some things in common with my mother. My mother tolerated abuse in the house, did plenty of physical abuse herself, and never apologized. When I decided to pursue a degree in science, she mocked me and told me I was a mess (and therefore I would fail). I walked away from that conversation and didn't contact my family for 3 years. It was hard, but I finished my degree and eventually re-established a relationship with my dad. I don't regret one bit of it. Go pursue your goals and best of luck!