Girl crush haaalp!

I have a crush on a girl on my field hockey team. She is super nice and teases me sometimes but she also seems to act this way with her close friends... but we aren't really friends. Does she just want to get closer? Or could she maybe like me? I'm really bad at reading signs. I also don't know if she likes girls *in that way.* So, do I tell her I like her, even if I don't know if she likes girls (btw, I'm definitely not popular and I'm not sexy or conventionally attractive, but I'm nice and a lot of people like me). What do I do?!