So, she gaslights you, makes you anxious waver between hope and distress, and tries her best to make you feel like your opinions and thoughts are 'wrong' because they're not hers. I think you've named it perfectly - she's trying to nibble you...into her own shape.

I don't think there's anything wrong with dropping the rope with family members (or anyone else, for that matter) who are painful to be around. That doesn't have to mean that they're a bad person, just that their dynamic with you isn't healthy for you.

I have done a similar thing with my two brothers; it was painful for me to try to have with them the kind of relationship I thought siblings should have. I dropped the rope, and now I reply if/when they email or text me...which is maybe once every 6 weeks for one, and once every 8-12 weeks for the other. I don't hate them, and I don't even think they are bad people. The kind of people they are, though, is not healthy for me when it comes to investing in a relationship. I feel much less stress in that part of my life now. I don't feel like I need to bring it up to anyone at all. Honestly, I don't have any idea whether either of them have even noticed. It was more about me changing my behaviors and emotional investment in those relationships than drawing a line in the sand with them. It has had the byproduct of clarifying how/why they communicate with me, which has also been beneficial in making me feel OK dropping the rope.

I hope the space you're creating for yourself now is beneficial to you, also. You deserve to develop relationships with people who feed and nurture you and your soul, family or otherwise.