I made a friend coming up 2 years ago from facebook, we’re both females i am 19 and she is 22, and ever since i met her she has gradually became me, down to claiming she has the same exact mental illnesses. Everything is a competition and even though she has a boyfriend she still doesn’t like when i get any attention from males or god forbid they show more interest in me than her. 

It’s ironic because I struggle severely with my identity, so i take things from people i meet or online but to experience it myself so full-on, it’s a different story. 
I have always been quite alternative/gothic which is extremely rare where i live (rural town in northern england) but since she’s been friends with me she’s changed into my style exactly, she posts photos in the exact pose i do with exact same outfit, i wear weird stuff and she has never ever wore that stuff before so i knows it’s because of me. I also have green eyes and she now wears green contact lenses everyday aswell as my style and she also got tattoos which were a big part of my personality, and the other thing was cats which i love, she said she hated them when i met her but now she got a cat. I have an extremely abusive ex that i told her about and i remember telling her about him, he had a weird obsession with vikings and motorbikes, he follows her on instagram and nothing else and she started randomly posting viking and motorbike related stuff only on her instagram? /: 
I’ve been open to her about my BPD since i knew her and recently found out I have ADHD, she has been in an autism diagnosis waiting list for 2 years and finally got in 2 weeks after i was diagnosed with ADHD, and she came back with them saying they think she has adhd, and she told me that she thought they were also hinting that she had BPD. 
Also whenever an attractive guy comments on a facebook post of mine she comments under it and when she was single she tried to make me look bad if there was a guy with us.
I don’t want to talk to anybody about this in my real life because it sounds like i’m jealous and trying to make her look bad because i’m not even that attractive, i would even say she is more attractive than me and she’s 4’11 and i’m like 5’7 so don’t understand why she’s doing it. but it’s really causing me distress because i also don’t know how to end the friendship, i don’t want her to see anything i post or do anymore.
Another weird example of something she did was after i told her a guy had been sexually harassing me online and sent me pics without my consent she kept showing me who she was talking to and saying she thinks they’re trying to be weird with her because he sent a picture of him flexing to her.. but then proceeded to send him a picture of her cleavage with writing over it. It’s like everything that happens to me she wants to happen to her too?