Well I have to agree that this girl was rude. Frankly since she is just a colleague and not someone you need to maintain relationship with ( I have rude father and rather rude sister in law but it's hard to escape them), you can avoid her company. Or next time she is rude just speak up. You can't really change rude people though. I think you need to work on your own confidence and self esteem as well as other skills ( communication etc) as we can only change ourselves. Please do get professional help.