If she's open to talk to you, the chances are she likes talking to you.
If she's shy, then it would make sense for her not to approach you or say an awful lot in conversations.
Your task is to get to know her better without coming on too strong. Maybe sit with her at lunch a few times if that's possible. Or next to her in class sometimes. Be part of her group or her partner in a project. Or even after class just approach her. It's good that you have talked to her a bit already and that you have a class together because you can always use the "what's the homework?" and the "do you understand this?"
Every small conversation and time spent around her will help her to feel more comfortable around you and at some point you can ask her to hang out with you outside of school a bit. Half her friends, half yours. And then work your way to just the two of you. If she's shy, you're going to want to take things a little slower than you usually would, but not too slow!
Also, try not to over analyze everything she does. It's a trap that we're all vulnerable to when we like someone, but must defend against.
:)