Ex-best friend

So I used to have this best friend and we saw each other basically everyday and we used to always say we would never stop being friends and we were like sisters. We had this massive argument about something and she decided she didn’t want to be my friend.

Since our friendship broke she has been really horrible and has taken most of my friends. She has become best friends with 3 of my ex boyfriends and is apparently dating 1. Is it bad that it makes me angry to know she did that or should I forget about it and move on ??