Hi. Gosh that sucks that this happened, especially in the thoughtless manner it did too. I realize she and the relationship were really important and meant a lot to you but consider yourself fortunate that this happened only a month in. Imagine this happening after the investment of more time especially once routines become more established. How difficult it would have been if you'd had a relationship with the children.

There are a host of possible reasons why she would go back to her ex. Women who are abused (physically or emotionally) may return again and again to their abuser. They do this for reasons that they may feel it safer to deal with the known than the unknown. Many abused women are made to feel as though they are not worth anything more than their abuser and are in effect tied to them. Perhaps being told what to do by her ex is so ingrained she is scared of what he will do if she doesn't follow. Maybe she is scared of what he will do to you. Maybe she feels her children are in danger.

So, this breakup may have nothing at all to do with you or how good the relationship was.