Hehe, I've been down that road before...trust me, it is not easy.
I was trying for years(!) to interest my wife in computer games, I had no luck what so ever, because at that time I was mainly playing shooters, which my wife absolutely has no interest in. All in a sudden I came across Diablo II (yes, it's about five years ago since I got her into it). I never really have gotten into RPGs (I know, it's hack'n'slash) before, but this time I suddenly got hooked. I showed this to my wife, and lo and behold, she said "Yeah, might as well try that one".
Actually, you know what got her? The music and the isometric view. She really liked the music (we both like it very much, I think it's much better then in the expansion pack and in WoW) and the isometric view made it easy for her to earn her ropes (she gets easily lost in the real world, 3D-games at that time would've been impossible for her).
Once we got the ball rolling, it was easy for her to slip into NWN, then into KotOR, and after that we had our first try at MMORPGs, the infamous Star Wars Galaxies. We loved that game until the great nerf came, the NGE. By that time, the whole world was getting into WoW, and so she was actually the first of us to try it.
Since then we've been playing WoW as a couple since Dec '05, almost every day for at least an hour, usually two.
One advantage my wife has, she really has great imagination, and loves fantasy stuff. So it wasn't too hard to sell her on fantasy RPGs. She still has no interest in shooters, but that is ok, since I lost my interest in them anyway.
Our first duo in WoW was Shaman/Mage (she Shaman, me Mage) and that rocked pretty good, although we were both completely new to the game. These are still our mains (both 60), currently we're playing a Druid/Priest combo (she Druid, me Priest). That works very well as well, although the massive damage output from the mage is missing. These are our main twinks (lvl 40). We have also two other evolving duos (Paladin/Warlock and Hunter/Paladin, the latter our only Alliance chars). Both teams are in their early teens.
So, the question is, try to find the right(!) game for her to get in to computer games. For my wife it was Diablo II, isometric view and the music(!). Maybe it's WoW for your wife, but I would try more than one game.
Hopefully it works out, but then you may not want to know how your whole marriage develops after that....