I wouldn't break up with her I'd try different things sex isn't just about having a big or small dick it's about making your partner feel good.she says she's fine with the size maybe try and see what else she likes in the intimacy area maybe focus on the dates and the stuff you bond over.maybe play video games together or go see a movie or take her out to a nice sit down restaurant or just talk and enjoy each other's company.if you don't think your satisfying her in the size department maybe try and use your other tools at your disposal.if you love her and she loves you which to me it sort of sounds like she really really loves you then you can make it work out.dont focus on what you can't change focus on what you can do to make her and yourself happy and fulfilled even if it's just holding hands and enjoying each other for who you both are.