Maybe you guys could go out as a couple and meet new people. Since she doesn't have any interests or hobbies, pick one of your own and attend some related event/venue and be friendly to other people. Also, if she has no interests or hobbies....what does she do for entertainment? Take a closer a look and figure out if there really is some sort of interest in something....anything. You might have to dig deep and be creative...like if she watches Game of Thrones and it was feasible to attend comic con and attend the cast panel, something where you really have to make a stretch with your imagination. It could be totally random and tangential too, like if you couldn't attend comic con, but there happens to be a comedy club nearby. That's just some ideas that might help to increase her socializing. But, the real issue is the ex, right? It's so common for exes who remain friendly with each other to screw up subsequent relationships. Especially by having an active friendship during the early stages of a new relationship. It's likely that her ex will probably deal with this if he gets a new girlfriend who won't be warm to the idea of their friendship. Your girlfriend and her ex forgot to move on. You being upset about this does not equal controlling her or being unfair. So, how many years do you wanna be in a relationship with these two people? Do not sacrifice your happiness because these two people can't let go of each other. Decide what you want. If that's a relationship with a woman who is not friends with her ex, then that option is not available with your girlfriend. Don't be afraid to break up because of this, you're 21 and there is plenty of opportunity available.