Sorry it took me so long to respond to this, but I had my bachelor party this weekend, and to be honest, I still don't feel right.
Anyways, Jessica, I don't feel like its necessary to blatantly state that school is your number one school. If you've written well informed essays, that show your diligence about the school, and you've interviewed showing your knowledge of their program, they will not think you only consider them a backup. If your essays were weak and looked like a copy and paste job, then I'd be worried. Personally, I never mentioned anything to Emory about other schools, but I also never said they were my only choice either. I just didn't discuss that with them. I visited the campus twice, sat in on some classes, met with current students and alumni, and I feel it showed on my application. They knew I was interested based on my application. To sum it up, I think you'll be fine, so stop stressing. Most likely the school is not going to turn you down because you're way overqualified. I would tend to side with the argument that they'd be more willing to take a chance on you to improve the quality of their class than worry about yield. Best of luck.