Boyfriends female best friend

hey guys! So just to clear this up to start with I have absolutely no problem with my boyfriend having female friends I encourage him to have a seperate life from me and given he’s been friends with her longer than we’ve been together (together 5 years & 1 month).
Anyways,this female friend is absolutely awful she is bitchy and talks about EVERYONE (even her “best friends” that are also female). She absolutely hates me and for no reason? We’ve met multiple times and she has never argued with me only once in a phone call when I called my boyfriend when he was at her house for a few drinks with other friends. She always tells him I’m horrible and that he should break up with me (even before this argument we had one time) and she’s always saying that he can do better and that I’m fat and ugly? I honestly don’t know what to do? I would never dream of telling him not to be friends with someone but I just wish he’d tell her to stop with the name calling when she doesn’t even know me? I don’t wanna cause friction with his friends but I just feel really disrespected. I hate to be that kind of girl but I feel like she has a thing for him maybe that explains why? Idk how to approach it without it becoming an argument with her or my boyfriend because that’ll make her hate me more