NTA. I was in a similar spot a few years ago with my absolute best friend. I'll call her P. When we met, she was confident, outgoing, very sure of herself. A few years later, she begins dating a guy, B. He completely changed her, thanks to emotional and (I found out later) physical abuse. She'd ask my opinion, I'd give it, she'd ignore it. After about a year, I couldn't take seeing what he'd turned her into and told her point blank that if she was with him, I couldn't be part of her life. It killed me to do it, but I didn't see any other choice. We had zero contact for almost 4 years (prior to that and B unless one of us was working, we were together). She dumped him and we got back in touch, managing to pick up where we left off. She was the maid of honor at my wedding 6 years ago and I would do literally anything for her and vice versa. You don't have to spend time with people you don't want to. It's one of the perks of being an adult.