RELATIONSHIP FADE OUT

( long post..sorry ) My best friend and I have been close for around 4/5 years. We met at school aged 15 and spent the ages of 16-18 getting wasted together and fighting our way through adolescence. Now we are almost 20 and I think the friendship peaked a while ago... There have always been issues, she slept with my ex boyfriend ( we were 16 ) and I didn't find this out until over a year later and I had already broken up with him by this point; I felt so much hate for him it seemed pointless to hate her too (stupid of me, I know). Anyway the main issue at present is that she seems to copy or imitate EVERYTHING I do (clothes, music, style, hair cuts, even pushing herself into my other friendship groups that I have formed since she has been at uni and I have been on a gap year) I'm happy to share friends with her but she doesn't have much in common with them and it feels awkward when we are all together. She also has subtle ways of lowering my self esteem by critiquing my hair/make-up or fair skin (I usually love my pale skin but when she says I look 'ill'  I feel like a lesser being - if you ever ask her if your outfit looks alright, she will probably say 'hmm try a different top' then when you try another top she'd say 'actually no definitely not, just wear the other one.' And then I feel like crap) Another issue that seperates us now is that when we were younger, as I mentioned before, we would party together, smoking weed or drinking etc but I stopped smoking when I was 17 and she still continues to smoke (and enjoy other things) even on casual nights out or at gigs. I feel like I can't connect to her anymore; I read books and go on breaks with my boyfriend while she spends 80% of her time online shopping buying shit I've already got or taking drugs with HER boyfriend. The only thing we talk about now is 'do you remember that time when....' And then have some dark conversation about the meaning of life- I appreciate these weird chats which is the main reason we've stayed close... 
Has anyone else ever outgrown a 'teenage' friend? Or been outgrown even...? Should I try and limit our time before I go to uni in a couple of months? Or just wait for it to die out naturally...