He's cheating on her but she wants to believe that he loves her like she loves him so she convinces herself to believe his lies. And she had hope for their love and when he broke up with her he crushed that hope. She still loves him after that so she calls him all the time and still tries to talk to him, but around his friends this guy plays it off like "she wants me shes gotta get over it cause she can't have me, shes so annoying" trying to be cool. He still talks to her though and to make herself seem less pathetic she pretends shes perfectly fine and confident without him. But he knows shes not over him. And so she finally decides to give up on him and starts dating another guy. Now this jerks sees them together and wants what he can't have. He just thinks he's sorry.