Ugh, grad school applications, amirite?

Before leaving for China in the spring, I did all the research I could on the programs I wanted to apply for this fall and I met with the two professors who I felt would be the best people to write my letters of recommendation. They're both awesome and they agreed, so off I went on my merry way, thinking I'd handled that part and would just have to remind them when the time came. Well, the time has come, they have confirmed that they will write my letters and lo, I take another look at the requirements for my top program of choice and it now requires three letters of recommendation.

Now, I'm either crazy, or the requirements were changed since February. I know I would have noticed it back then, so I'm pretty sure they've changed. The other program I applied for only requires two letters. So, I urgently had to email another prof and beg for a letter of recommendation. I feel like such a jerk. I know this other prof really likes me and liked my work. She gave me an A+ in a fourth year class, she has to like me. But I feel like asking over email is rude. And I'm afraid she won't remember who I am.

Any academic GTers around? Was I a horrible rude person for asking over email? Anyone have other application horror stories? Let's freak out about them together.