Having a good show heifer not in calf is about one of the worst feelings in the world. Like others have suggested, the first thing I would do is get her to a vet (preferably one that deals with purebred cattle - if you can get to one that deals specifically with the reproductive system (does flushing, etc), so much the better). It is best to rule out either reproductive or disease problems right from the start - At least then you won't be wondering.
That being said, if the heifer is not in calf now, it may be a big signal of trouble in her future - Not being able to get in calf as a bred heifer usually means things are reproductively not quite right. You may get lucky by keeping her over...but usually, you don't. I think the key is asking yourself some tough questions about your goals with your heifer and your herd. If this is a fertility issue, is that something you are willing to risk incorporating into the genetics of your herd in the event that she does get pregnant in the future. If she had a whopper of a steer calf, you may be home free. However, If she has a heifer calf of saleable quality, you have to consider whether you would want to put someone else in the position you are in now. Would you be willing to risk selling a heifer calf that you knew had the genetics to possibly be a non-breeder and then having to replace her or refund the money? If you kept her, would you be willing to risk feeding the cow for three years till she has a calf, and then feeding the calf for another year and a half to find out her daughters are infertile as well. Would you be willing to risk the damage to your reputation (and therefore pocket book) if you sold a bull out of her that sired daughters that couldn't get in calf. As the saying goes, sometimes your first loss is your best one, and at my house, not getting in calf as a yearling heifer on a good ration would be a first class ticket to the trailer. Nonetheless, If you are raising cattle strictly for the show ring, and feel she could raise the next great market heifer or steer - thus the only thing you are worried about your cow passing on is her phenotype (it sounds like she is pretty great in this area) - then reproductive soundness is not your concern and keeping the heifer over an extra year might be a small risk for you to take.
Best of luck with your heifer and here's hoping its just an infection as DL suggested.