Ichi, I'd wait a few more days and then just send her a casual email saying "what's up? just seeing if you still wanted to do lunch", something really quick and casual. And if she doesn't respond to that, fuck it.
I've been emailing lots of girls lately too, and attempting conversations with them, it's amazing how after 3 or 4 emails, these girls can cut you off. There was one girl who was a guitar player and anthropologist, who had a really cute picture up (nice blue eyes and light skin tone, looks very Irish), the emails were starting to get pretty long and detailed (4 or so emails back and forth to each other), and I said that "we should hang out when I get back from Miami" at the end of the most recent email to her. No response tho

I sent another email out to another girl I've been mailing back and forth with, with the same line... and gave her my cell #. So we'll see if she calls or gets back to me, she's a cute, Italian-looking brunette who loves to travel. So far, the biggest prospect for me is this one girl who's a PA at Stony Brook, who spent her spring break at a friend's house in Virginia playing Galaxy all weekend and loves Chopin (she seemed pretty impressed when I namedropped some Chopin songs and stuff I learned from Eternal Sonata

). She is thin, and blonde...