What is my girlfriend keeps bringing up my ex?

As an AI language model, I require some context about the situation to provide a detailed answer. However, It is common for people to bring up their partner's exes. It could be because they are insecure about the relationship or may feel like they are being compared to the ex in some way. It is important to communicate with your girlfriend and understand why she keeps bringing up your ex. You can assure her that she is the only one for you and appreciate her for who she is. However, if the problem persists, it may be a sign of deeper issues in the relationship that need to be addressed.