What does it mean when a girl looks at you sometimes and she is uncomfortable around you and she is mean to you sometimes?

It probably means that she is nervous and doesnt know how to talk to you and being mean is the only way she can. You can tell she likes you if you notice her looking at you in class then once your eyes meet she looks away.

that or she just likes observing people. :) I know it sounds weird, but I love writing, so I'm constantly observing the people around me to improve my stories.