Thank you both. Talking to her about it would only create trouble. And I don't know if I truly understand her behavior. It just makes me feel like she cares more for her grandchildren (one of which is grown) than she does her first born. Her adult grandchild, M, doesn't respect her and just uses her. But she drops everything for him. I just have to let it go. It's a sad situation. And I agree, some distance is probably best.
I've been reading a WikiHow post on how to deal with rejection from a parent. It has a lot of stuff that's helpful.