First time role playing, how to I address this problem?

So I am brand new the role playing as I am really shy and normally don’t like to tell my stories to other. I am role-playing with my friend and her siblings and I have a problem. I have added my character into an already existing, huge lore, place. And my friend is trying to make my character do things that would not fit my narrative. For example my character has a boyfriend and this guy is very specific to her background as they are kinda tied together by fate through different lives. Every time my OC dies, she will meet her boyfriend in the next universe, her could be her lover, friend, or enemy. My friend forced me to break up with the OC’s boyfriend and now is trying to forcefully get my OC to date a girl. I told her this character is strictly heterosexual and honestly is really mainly attracted to her boyfriend but my friend will not listen. I have other OCs who are LGBTQA+, but she is so admit on the straight one. I don’t want to cause trouble but they are constantly forcing my OC to do things out of character that I have created because she is my character. And I don’t know what to do? I don’t want to be mean or cause drama but I am stuck!