I would give her another chance if she is asking for one. Some men aren't famous for working on their relationships so it's quite common for the woman to feel taken advantage of. You two need to sit down and talk things out. If you feel her reasons for being flatted with attention by someone else is reasonable then you both need to pull up your socks and start working together. How hard did you try in the relationship? How hard did she try in the relationship? These are questions you are going to have to find the answers to and the only way to do that is by sitting down and talking it over together.