The fact that she stares at you is enough to say she might be interested, why else would she looking at you if she didn't found you interesting? The fact that she doesn't holds eye contact does not have anything to do with the fact that she's interested or not but more to do with his personality, she could be shy, or not that confident or she could just be scared to feel vulnerable and let you know she likes you.
If you like her you should AT LEAST talk to her, what do you have to loose? If she's not interested after all, you'll at least have made a new friend at work, that always come in handy right?
Shes probably shy, and think about it, if there's a person you really like or are interested in and they catch you looking at them, wouldn't you feel a little embarrassed and look away. defiantly pursue her and have a chat, you never know where things will go!
Women, generally, don't stare like men. If she's checking you out that is the woman's first move. You have to make the next move and it's very uncomfortable because men fear rejection. The next step is in your court now. Make a move or walk away.