Tempoary account because I don't want my bf to see this.

My bf(19M) has this stupid thing about him where if he likes or develops an interest in things he will hyperfixate on it, what's bad about this is he tends to make the thing his entire personality which is annoying. Recently for example he picked up a book i don't remember what it's called but i do know it was sci-fi, he posted memes, made refrences to the book and acted like how the characters would act in the book like praying to the fridge so it may cool his beverages faster and it won't stop there he always wants to initate a conversation about the book with me since he has no one else to talk to about it.

So to make him stop I stopped talking about things I liked with him entirely, If I can't talk about what I like he can't talk about what he likes, simple and fair yet it quickly bit me in the ass, one of my university friends(21F) who is a bookworm took a liking to the book my boyfriend was reading and engaged in a conversation with him, i told her to stop because he will go on and on but she sat there and talked with him for hours about it.

I thought she was going to get tired of him too but somehow they exchanged numbers and started giving each other book recomendations. it didn't stop at reading eventually they recommended shows, games and movies to each other, what has me annoyed is that they went and saw the new deadpool movie and are acting friendly with each other like brother and sister.

I don't like how things turned out and I want to confront him but I don't want her to say it's my fault for being "Stubborn"

AITB if so what can I do to improve