Bisexual

I’ve just gotten out of a 4 year relationship with a boy. I starting to Catch feelings for a girl. I told my mom and one of my sisters about being bi and they were cool with it. My other sister doesn’t know but today she was making jokes saying she can see me dating a girl during college and making rude jokes and saying being bi runs in the family and she also said she’s always thought I was gay. I don’t feel confident in telling her. What do I do because I wanna tell her but she made me feel some way