Can I safely ume this really shy girl likes me?

yeah, she likes you. Invite her to a school function like a football game, a drama play, or an art show. That way it's not totally awkward, she can tell her parents she's going to school for (insert event here) and they won't worry. Then just talk to her more and try to get her to open up to you... best way to do that is to tell her how you feel.