At the end of the day, you have to decide what is and isn't worth compromising on.
If you can afford it, wouldn't mind having your sperm used to produce children, and it won't delay other things that are important to your physical and mental health, obviously bank the sperm. That solves problems. But depends on money.
If you can't afford it, or it would delay things, then you have to decide - is her wishes or your needs more important? Can your needs wait and you remain healthy mentally and physically?
If you don't want to have children...well, I think that's your right too, but I probably wouldn't suggest hooking up with someone who wants them badly.
I would be concerned about two things, however. First, if you and her have different ideas about having kids, that could be a problem. Second, I could see someone using this as an excuse because they really want you to have the body you have today, not the body you'll have later, and perhaps they think if they can delay it then they can stop it. That wouldn't be a good relationship to be in.
I'd also remember that plenty of people are sterile to begin with. Would she not date someone who was sterile? I know some women wouldn't, and I won't pass judgment on them, but I probably wouldn't want to date one that valued me most for my sperm.