I know for sure that she likes you because when i see my crush im always startled and look away as quick as i can. Thanks for asking cool questions!
Either she's trying to flirt or you have something on your face :)
she likes you.
For me that is an easy question, first maybe she has a crush on you or she is jut shy to look at you or ur just weird.
Maybe it's because they like you, but they are shy.