I know I'm not Zee Bee, but I do have some advice.

You shouldn't let them blackmail you. Tell them that you are not doing what they want, and when they try to blackmail you, say you don't care. It's fine if people know your bisexual, theres nothing wrong with that. If I where you, I would not call these people your "friends" anymore. They would stand up for you and treat your decisions with respect if they where real friends.