my (18f) and my boyfriend (20m) have been together for just over 4 months but have known each other for a year. he’s had this girl friend, going to call her b for convenience, for just under 10 months. i don’t know if they have flirted or messed around in the past and my boyfriend denies anything has ever happened between them, but b has always had an infatuation with my boyfriend. she is constantly making posts about him like they are dating. i have never tried to control my boyfriend and i don’t care if he has girl friends because i trust him completely. i’ve tried bringing up my feelings but he says they are just friends.i wanna trust him and let him have all the friends in the world but all of my friends are telling me it’s a big red flag and i don’t know what to do. i don’t want to be controlling but i don’t want to continue to be uncomfortable because i can’t trust this girl
tldr- my boyfriend’s friend acts like they are dating and i don’t know how to respond without being controlling.