Angry about ended relationship

[ztigerb]

FYI I'm a senior in high school and I just turned 18.

So my first real relationship started during spring break of my junior year. It was good and fun in the beginning. This girl was someone who I worked with in Stage Crew. So we had that in common, but it later became apparent that we had nothing else in common. She had no reason to ever hang out with my main group of friends, and I had absolutely no reason to hang out with her group of friends. Somehow the relationship lasted the summer and into my senior year. A few weeks ago I realized that it was going absolutely no where and I had no real reason to continue putting in the time and energy to keep the relationship alive. So I broke up with her. Now she is days or hours away from being my friend's girlfriend. This friend is part of what i consider a secondary group of friends. She essentially attached herself to my friend (interestingly the same way she did with me).

Anyways I want to be friends with my friend, but it angers me to no end when I see her hanging off of him even when I know I do not want to be in his place. Any thoughts or ideas on the subject of friends and ex's would be appreciated.