I'm sorry that this has happened to you, just remember that she is a human being and as happy and proud of you I'm sure she is, everyone has a limit. Sometimes our emotions can be bigger that we ever thought as trans people-sometimes we get more angry or depressed than we thought we sounded and it can cause people to become distant or become hurt. Remembering that she has her own mental health to look after might help you heal. It's normal to be upset, take as much time as you need, but also distract yourself from it. Don't dwell on your past relationship or promises. Your transition is about you, and having a support system is great, but our biggest support system is ourselves. Don't give up. Let yourself be sad for a little while-give yourself a time limit and then just make appointments so you know you need to do it.