She keeps bringing up her ex.
This means one thing. She is not over her ex. If she can't stop talking about what an awful or awesome guy he was, it's bad news for any future you would have with this girl. It's like that person who says that they hate the new Taylor Swift song, but every time you're around that friend, they sing it. If you hate it so much, why is it always on your mind? It's because deep down, you love it. That doesn't bode well for dates or Taylor Swift songs.