I mean - she tells you she wants to have kids one day in the future, you just say that's cool, tell her you don't want kids or whatever, she should say that's cool, and you move on with your day together. It doesn't have to be this dramatic revelation that sends your relationship reeling, "we can't get married bc she wants kids, why are we together if we can't get married" like holy shit, any given person you are dating at any given time is probably not going to be the person you are dating in a few years, but also they might be, probably not but there is no way to know, that doesn't mean you can't have a nice rest the summer together or w/e. You're just fucking around with someone, it's fine. Stop breaking up, you're barely even together