My best friend and I recently started college together as roommates. One weekend we went away with some friends, including a guy I liked. The next thing I know my friend is holding his hand and dancing with him. I tried not to let it bother me because I know she would never do anything to hurt me. But a few weeks later she was again flirting with and monopolizing a guy she knew I had an ongoing relationship with. We didn't talk about it because neither of us wants a confrontation. Now she's mad at me for not helping her get a job where I work, as I've done in the past. I don't know what to do.
You're getting a first-rate education in relational bullying. Some girls are really good at this sophisticated means of mean, and friendship with them is toxic. You can solve the immediate problem by not confiding in Ms. Mean (confiding gives her ammunition for betrayal), seeking a new roommate and moving out ASAP. But bullies don't pick on just anyone. The failure to discuss with Ms. Mean your discomfort with her actions is a clear signal that you don't stand up for yourself, and that's her ticket to manipulating and hurting you through dealings with others. You won't find a relational bully in every classroom, but you will need to know how to speak up in all your relationships now and in the future. Assertiveness does not require confrontation. Without making blaming statements, speak clearly about what you don't like and how it makes you feel. Then make a specific request for change. ("Please do not flirt with my boyfriends" is a reasonable request to make of a friend.)