What should I do???

So... At the start of september, we were put in new classes. So I was like "oh, I'm just gonna get on with my work and just ignore everybody like last year!!" But there's this girl in my class that I knew her briefley, but since she's in my class, I have to spend more time with her. I really like her now. My problem isnt that I'm scared that she's not lesbian or bi, and is gonna freak out cause I already know she's a lesbian cause she's said so. I'm scared about coming out to my mum and friends. I've already told her that I like this girl, nut she said that she had feelings for a girl when she was about my age to. But she's a straight person. It felt like she was saying I'm not bi just cause I like this 1 girl. Idk how to properly come out to her. Ik the girl I likes has a gf bit I'm now more worried about coming out to people. Any help?? 😥😥😣😣