To combat this, you'll need to break contact for a while.
Remind yourself that this is a temporary but necessary part of winning her back.
Her friends will be there for her, but friendship can only cover some of the emotional needs of a girl who's feeling hurt and rejected right now. Being there for your exgirlfriend after her new romance has failed is a huge step toward winning her back.
You're in a strong position, and she's weak, tired, and emotionally spent.
If you're willing to wait that out, your ex is going to be single again. When a rebound relationship ends it's usually the girl who gets hurt, and when this happens your ex is going to be looking for some comfort.