My suggestion would be 1,000 point lists (as this is closer to the normal 1,500-1,850 point games you see). This should give her a feel for it. I would go over the rulebook with her briefly, then play two or three games, then I would have her reread the rulebook, but more extensively. I found when I was teaching my new buds
40k it was much easier to apply the rulebook after I had walked them through a game or two. I won't lie. The first few games will feel like you are playing with a toddler, and you may even have to help her tactics wise, but the most challenging part about
40k is learning not only your own army, but the armies you encounter on the battlefield. When I got into
40k I went to MiniWarGaming over on Youtube. (They also have a site, but I find the Youtube interface more friendly and easy to maneuver.) Matt and Dave (the owners/founders of MWG) do a great job with
40k. They have Battle Reports, Tactica Videos, a series called 'How to Play 6th Edition Warhammer 40,000', and much much more. You, even as a veteran player, may enjoy their painting tutorials and reviews.
Sorry, I know that is an unappealing block of text. The
TL;DR (too long; didn't read) version:
1st.- Go over the rulebook with her very briefly.
2nd.- Play a few games with her. Really walk her through everything.
3rd.- Have her go reread the rulebook. (It is tediously long, but she can skip the fluff)
4th.- Play, Play, Play
5th.- Point her towards online resources, DakkaDakka, MiniWarGaming (On Youtube), or plenty others!
And remember, maybe let her win a few times. Happy wife = Happy life