Congrats to the two of you ;)
One thing I do suggest you do asap, is get the suspension sorted out. Front is for a person about 130lb, and rear 170lb (something like that in any case). With your wife learning, it really will pay to set up her bike for her, especially if you want her to carry on with it.
How tall is she? If she's struggling with the height, consider longer dogbones (do a search for threads on this, there are many). One more thing, she won't be doing any long rides for a while, so don't fill the tank right up - it really does make a difference when you dump it. Make sure she also knows the right way to pick the bike up, so she doesn't wear herself out (not always possible, but it usually is).
One thing I've found help me with confidence on the bike, is working on it a bit myself. (admittedly I rarely touch it these days, but I'm generally confident enough to know what's wrong if something is - not always sure what the heck to do about it though). Just basic things like changing oil, air filter & knowing how to change a spark plug is a great start.
I hope that gives you a few ideas & get your wife to join DRN - the more women harrassing you guys the better ;) lol
Also, check out Cindy Gross's page about learning to ride
http://cindygross.tripod.com/dirtbike.htm