Your story looks all good. I think today would be a good day to send her a mail, she's probably waiting for it.

As for the mail, my advice would be to start stating that you had a good time with her last Saturday. You could follow-up mentioning a topic of common interest you discussed last time, and ask some questions about her, so that she is inspired and has fodder to write a reply.

Depending on how both of you relate to e-mails, writing could be an important part of your exchanges, at this moment. But in any case be sure to maintain your contacts bound to real life. To do so find a reason to see her again: either bring her some CD, movie about something she doesn't know and might like, otherwise just invite her for a drink, whatever. Try to organize a meeting for this week or at the latest next week/week-end.