She might like you, or she could just be the shy type, or both. I know I do that when I'm around the guy I like, actually, and I try to avoid them. It's not really intentional, but I just seem to get super shy around guys that I am attracted to. It's really just to hide how I really feel or think about the person without giving anything away or looking like an idiot. It might be the same for her. If your are interested in her, make the first move and try to find out what she thinks about you.