Congratulations! Ironically, I'm in sorta the same boat. My wife discovered that some other friends of ours, that we had no idea were gamers (we're not really close friends). She jumped in and talked to them, mentioning that I gamed, and before we knew it, she had kinda sorta committed to playing with them as well.
It hasn't happened yet, and I don't have high hopes that she'll really pick up the hobby the same way I have, but I'm really interested in showing her what it's all about, at least, and hopefully she'll at least have as much fun as she does playing Skip-bo...
Anyway, for suggestions, I'd go through some character generation with her ahead of time, and make sure she's as up to speed as can be before she starts. Nothing worse than sitting there not knowing what you're doing. Maybe even run her through a small trial scenario of some kind just to show her how a few things like skill checks, simple combat, spell-casting, saving throws, or what have you work before the session.