First make sure you are covering all of the basics that involve sleep:
-no coffee/tea/apples/other foods/drinks that keep you awake anytime past afternoon
-make sure temperature of bedroom is conducive to sleep - sometimes making room a little cooler so that blanket is needed is better for sleep
-make sure room is as dark as possible
-dim the lights about 30 minutes before bedtime (bright lights right before bed does not help with going to sleep)
-exercise helps you go to sleep and get a better night sleep
-make sure bedroom is a place of relaxation (should just be used for sleeping, not working, not working out - only associated as a place of relaxation)
-make sure bed/mattress isn't interfering with sleep
-try to find out cause of bad sleep/staying awake (could be other things are on your wife's mind?)
If all of the bases above are covered, you can still try a few other things:
-relaxation techniques that help with going to sleep - relaxing one muscle/part of body at a time
-eye techniques - exercise your eyes by looking up, down, left/right. This is extremely effective if you try to look in the extreme peripheries of your eyesight and try to concentrate on an object for 30 seconds (your eyes will tire very quickly). Try this looking up left for 30 seconds, then up right for 30 seconds, and keep repeating until you don't have to look away.
-mind exhaustion exercises - find a way to exhaust the mind such as mental math (2x2 = 4, 4x2 = 8, 8x2 = 16, 16x2 = 32, 32x2 = 64....) See how high you can go and don't give up. Or try to recall the names of all 50 US states.
-change diet - if your wife is eating too many fruits, then this may be an issue. Fruits are great, but contain a lot of natural sugar. Try to eat foods with as little sugar content as possible - maybe try to just eat chicken, fish, and veggies for a day and see if this helps with sleep. Trust me, very difficult to gain any weight by eating just meat and veggies.