There's this girl in my science class who I have been trying to figure out if she's a lesbian and into me for the ENTIRE YEAR. When I first met her I was kinda like, "eh she looks really cool but I'll probably never talk to her". We now talk everyday in class and I look forward to the class just to see her, but I can't figure out if she's a lesbian. She ALWAYS tries to make conversation and small talk with me and even asks questions to me over and over just to talk to me even though I know she knows my answer. I also always catch her glancing at me everyday and when I purposly look away she keeps looking into my eyes. She even waits for me everyday to walk out of class together. If she is a lesbian, awesome! Because I wanna go for her!! I've literally been banging my head against a wall for this whole year trying to figure her out.
Maybe just try and get her opinion on gay rights or something. She might come out to you. Or you could just ask her out. You never know if you don't ask.
Just like the two others said, talk to this girl. You can only get to know it for sure when you ask her. You've lots of possibilities what you can ask - ask her directly that you've been wondering for a while and that you're curious, bring up general topics about LGBT themes, etc. Maybe flirt with her...see how she reacts, whatever. Just take the courage to do something that will bring you clarity