How to tell if a girl likes you?

Hey I'm a sophomore in HS and there's this freshmen i like but I've sorta ****** myself in that I used to talk to her before, I asked to a dance and she said yes, but the next day she said her mom "didn't want her going." Idk if its her mom being overprotective or if she didn't want to go with me but anyway we stopped talking after that. She always seems to be walking around with one of her friends when I'm waiting in the lobby or something, I think she's trying to get me to make a move. I think she likes me because she's very outgoing but around me she's quiet (I'm kind of shy with girls) and stares at quiet a bit at me. I had so many chances to talk to her since she's in my lunch and gym class but I was a freakin coward and was passive, she literally was looking at me and smiling almost beckoning me to her ( I'm fairly muscular if that helps with a mental pic). I would like to rebound from my stupidity and get to know her at least before summer. Sorry if this was long and thanks for reading this