Yes, it makes me crazy too. It's much worse than never having written in the first place. I used to actively have to distract myself (go out, not be home on the computer) after I had emailed because it made me crazy waiting for a reply.

If it helps, I think these feelings are pretty common (at least on PC). I just try to remember that it's probably not personal, she just hasn't had time to check it yet.
And also, that emailing has its pros and cons, and waiting for a reply is just one of the downsides. On the whole, I continue to email because I find the pros outweigh the cons for me. Hope your wait isn't too long!