Not everyone deserves love contrary to popular belief. Not everyone deserves to be happy. Some people don’t appreciate it. Some people are horrible people. Some people are dependent on relationships and are very immature and they are more focused on what they get out of people, rather than what they can give. They’ll continue acting like this and there is nothing you can do to change them. There is no saying what kind of person your ex is. It could be many of those things, however it could be the simple fact that you two just didn’t match. You didn’t get along. You can’t control or force feelings. They simply didn’t feel as strong as you did. Do not take it personally or as a reflection on yourself. You have to accept it for what it is so you can move on. Don’t worry about her new relationship. Worry about you.