I think you should not be mad at her. Even though you have every right to be she is your friend. Is e really worth falling out with a friend over? My cousin is presently in a relationship with my Ex-boyfriend, I fell out with her over it and I wish I didn't I would really love to still have her by my side whether she is with him or not plus if they break up your the one who gets to say "I told you so.. " stay strong with her through it all..
Felicialowe1217