Sometimes as we grow up we grow apart from people because we change. I know how you feel about growing as a person and your best friend hasn't changed one bit. One of my close friends back home, over the years I've changed my views on things etc and when I go visit her she's is the exact same person she was 5 years ago. Nothing changed, nothings grown and it's one of those things I've realized that she's not someone I could hang out with on a 24/7 basis not anymore. Sure she's helped me out a lot through my breakup and when I moved back home but in the end we're two different people, and two very different maturity levels. (some people choose to grow others like to be stuck in the same world they've lived in all their lives, without realizing it...)
I personally couldn't tolerate a very judgmental person around me at this point in my life, especially when I'm trying to change my views. Why should I make snarky comments about ex's new girlfriends being fat or anyone else when quite frankly there's a reason they're with them and not me. (that was just an example) I think you did the right thing in speaking your mind with her and even though you brought up past stuff, it's clear she hasn't gotten over it and continues to bring it up in the present maybe in different ways. Sometimes in order to succeed you need to get rid of the toxic people surrounding you along with anything else that maybe sabotaging or whatever your progress. Whether it's weight loss, new job, new place anything. There comes a time you just need to "break up" with people and move on especially when they are holding you back!