Good friend of mine was given this (paraphrased) response...AFTER WAITING FOR A RESPONSE FOR FOUR DAYS:
"Well, I'm waiting for a specific person to ask me to the dance, but if he doesn't, you're my backup plan."
First of all, how are you so sure that this mystery person will ask you? Not to mention that you noted that he's a senior, so what's the likelihood of him even noticing you?!
Second of all, you flat out told a really nice guy that he is your "backup plan?!" How would you feel if a guy told you that you were his backup plan if he didn't ask someone else?
Worst part is, this girl is my friend, but she's one of those people that it's difficult to talk to and convince of things.