She doesn't care about your feelings, so she will keep the information of her ex and talk to you about her ex. The reason is that you are not as good as his predecessor, which is the simplest reason. If you are really good enough, or if she cares about your feelings, there will be no ex at all.
Then what are you thinking? If it's a girlfriend who solves a problem, it doesn't matter if she talks to you about several exes. You're just one of them.
If you are a girlfriend who is in love and married, will you find it interesting if she casually tells you the history of her predecessor? Most people simply can't accept such a woman. They just advised each other not to share. You need to talk to the other person and ask her to delete her predecessor information and pay less attention to her predecessors. Or you need to settle down, even if the green light overhead is entangled in the end.