I experienced the same thing from a girl I work with when i first started, so did the next girl who started, and the next.. I think some people are just like that. They are hesitant to accept new people. After about about a year working there she is usually friendly toward me, but often gives me judgmental looks or whispers to her closest friend who works there and they giggle.

I've heard several coworkers say the same thing about her. She has her little click (people she's worked with for years) and doesn't want to let anyone else in. Several people have changed the time they eat lunch or eat it at their desks to avoid her accusing stares. Myself, I'm encouraging them to eat when and where they want. If she is uncomfortable with it, she can leave.

I try not to take it personally when she does this, although it is hard at times. It is not about me, it's about her. After getting to know her a little better, I have discovered she is in an abusive relationship, hates her job (even more than normal people do), yet lacks the motivation to do anything about it. It's a very common theme I've seen throughout my life. Miserable people tend to treat others in a miserable way.

I know it's hard, as I said it still bothers me from time to time even though she is warming up to me, but try not to take it personally. It sounds like her issue, not yours.