Speaking as the mother of a young child whose father was deployed for 9 months and a former regular army wife, I would say offer to babysit once in a while, and also be patient. She may not be interested in going out, or even talking, but your presence is appreciated and will help remind her she isn't alone.
Remember when events happen like lunches, parties, etc...that she might want to go, but will need help with the children. The hardest part is always trying to keep up some semblance of normality for the children and herself while husband/daddy is gone. Whatever you can do to help retain that normalcy will be a boon indeed.
Offer, too, if you have the time, to help with some of the daily routine. While getting out once in a while is nice, it's the daily routine and grind that drags down a mom in this situation. Sometimes just some help with cleaning the house or the laundry or chauffeuring kids or running errands is the biggest help you can give to relieve some of the stress and pressure. Especially keep an eye on her in case she gets sick (flu, cold, etc..) while he's gone; during those times she'll need all the extra help she can get and she'll appreciate it a lot to have someone to help her get through those tough periods.
Some wives like to talk about it, some don't. Just play it by ear and give her that ear/shoulder if she needs it but don't push it. I know I preferred not to give voice to my concerns because if I did, I'd end up breaking down and I hate breaking down.