If she's shy, it would be hard to find out if she likes you. Unless you approach her, talk to her, etc. you may not find out or take it as if she doesn't like you when in fact, she does, but she's too shy...
If she's not shy, she'll make eye contact, smile, she'll want to be close to you, she'll be happy when you're around, listen to you carefully, etc. etc.
