Excuse me here, but why do you need to get your wife into gaming?
Thing is, I've known plenty of women who have been coerced in various ways to play RPGs, and very few of them enjoyed it. Even if it relates to something they're interested in (like twilight).
And what's your end goal, here? If she loves twilight: the RPG, but still doesn't really get fantasy, are you going to always play this twilight game with her? Would that be fun for you?
I'm only asking because I personally have seen more than a few guys jump on the "I need to play RPGs with my girlfriend/wife" bandwagon because they thought it would be fun, and didn't fully think about their girlfriend/wife's perspective on things.
(and it's not just guys trying to get their girls in... I have a player that's been half wondering if she should get her boyfriend into gaming. Luckily, she hasn't tried seriously yet, and I hope she never does).
To answer the question at hand - something rules light, with powers thrown in. I'm sure FUDGE would work just fine. Hell, DREAD could probably work, too. Savage Worlds might be a good fit, or the d6 System (my personal fave, and the one I always mention).