Breakup and promise ring

Hi everyone.  I am new to this support group.  I am going through a very difficult breakup.  I am on no-contact now for 16 days.  Me and my ex were together previously for approximately 1.5 years.  I am separated with 3 kids.  The main issue she had with me was that I had not introduced her to my children from my previous marriage.  The main reason being that my ex wife feels as though she was responsible for the breakup of the marriage.  I wanted to wait until the kids were going to be accepting of things and did not want to rush things.  Unfortunately my ex girlfriend and I had come up with timelines that were not held up.  I did try to approach my daugther about the idea of me dating and it was not well recieved.  Unfortunately in the mean time things have changed and she now seems more receptive to it.  I have told my ex girlfriend this already and she has told me that it is too late.  We have been friends for about 5 years in total so we have grown to be quite close.  We do also occasionally work together.  I did give her a very expensive promise ring and after she broke up with me I asked for it back.  The idea of her still wearing this promise ring was very difficult for me.  She was previously engaged and kept the promise ring from her ex.  It was like an albatross for her and she ended up remodeling it into a necklace.  I never wanted this to happen to the ring that I gave her.  I now it seems rather cheap but it was not about the money and more about me trying to move on.  I am going through anxiety right now because of the promises that we had made to each other and the fact that everything has been flipped upside down.  I know the answer is for me to continue no contact and move on.  The problem is that we do work with each other and this can be very challenging.  I am really angry as well about things and part of me wants to be vengeful.  Lots of complicated feelings here.  I guess I am just trying to get by and over this.  I feel like my parenting skills are suffering because of the anxiety of the breakup.