Do you know the difference between liking a friend a lot and a gay crush? I didn't... AND ALSO I NEED HELP WITH A CRUSH. (15yr old girl)

Lol, thought I was totally bi, and I just realized that I've only crushed on girls. Thought I just liked some "girlfriends" a lot, like in an excessive way. Now I've just realized that had a crush on those girls (mind blown). Not sure I'm lesbian tho (might be demisexual when it comes to boys idk) but I'm currently crushing so hard on another girl (she's bi, and she knows I'm at least bi).So the point of the post is:Some young gay people don't know the difference between a bromance/liking a friend a lot, and a crush.Secondly I need help, I know from an inside friend that she's not crushing on anyone in her class (I'm in her class). I know you can't make anyone like you, but any tips on how to catch her attention, and maybe make her consider dating me?(Btw I'm already friends with her, and I don't wanna ruin the friendship)