THIS BITCH!!!!

So my boyfriend has a girl best friend that i’ve been nothing but nice to. Like i’m not controlling at all I let them hang out and im fine with the fact she wants him to take her to homecoming and everything. I’ve even tried meeting her in person but she doesn’t like me at all and now shes making my boyfriend choose between me or her...WHILE SHES WITH HIM!! and on top of that hes stressed enough already with other stuff like WHAAAT!!! Idk what to do like i know shes putting stuff in his head and we both mean a lot to him but she’s been there for him more than her but I don’t wanna loose him helppppp