How do I know if she likes me?

Hi so I have all the same classes with this girl I have a crush on and I'm trying to figure out if she likes me or not. We're best friends, but I'm non-binary and i haven't told her yet, so she thinks I'm just a girl. How do I know if she likes me as best friends or romatically? We've had moments were it was tense, like it would have been a good time to kiss her if she liked me, but we didn't ever talk about it. We always sit together in class, and we give each other things sometimes. How do I tell her I like her, and should I come out to her as non-binary before I say I like her, or should I say after? HELP!