Do you ever feel resentment/bitterness toward people? How do you deal with it?

Coming from someone who has been in the same situaton, the best thing for you to do, is tell them how you feel. You can only keep your feelings and emotions bottled for so long before you erupt and things get really nasty. The best thing is to tell her how you feel and ask what the problem is. They might not be aware of what they are doing when it comes to this. Just sit down and talk to her and let her know what your feelings are on the subject.