If she's stressed because of work.......that's the fundamental
issue which need to be addressed first......
Try to suggest to her to calm down a little, perhaps by cutting her
work hours a little bit. Slow down the work pace a bit.
Other than that, it's a bad idea to take sleeping pills for a long
time, because dependancy can set in.
For medication help, instead of hard sleeping pills, suggest to her
herbal sleeping pills, like the ones available OTC on pharmacies.
Melatonin, valerian roots, camomile, etc. Many pharmacies carry
herbal sleeping pills.
Also a good idea to drink a cup of full cream milk, at night. Full
cream milk hor. It will produce natural sleep inducing
reaction.
But I believe the best method is to relieve the stress.....so it's
best to take a short leave from work, maybe a little vacation.