The better question is why would YOU want them back? When someone treats you like this don't take them back. It can be both a understandable response to childhood trauma and abuse of your love and support at the same time.
Depending on their age, if they don't understand what is going on, and they don't understand the attachment style they have. It is impossible to work on this for them. They often need to lose "the one", realize it going into different relationships that suck so much they start to wonder why they can't have what they had before / with you, if you actually treated them right. Most people who have this attachment style will only figure this out after their 40's, sometimes around their 60's when they have been single for a long time. My recently broken up ex did this, but she was also very honorable about me. She basically warned me what was going to happen, before everything happened. We tried a LDR, but only bonded well face to face. It simply was impossible as she didn't want-want me, felt the situation was too difficult and already lied to her parents about me... which caused too much stress to fix.
