I would say you are right that she's probably picked up those habits in a stressful situation. Most horses will drop such vices when they are happy again, but windsucking is one of the most addictive and many horses continure to do it even after the source of stress is removed.
The first step I would take is to make sure she is happy in her environment, otherwise anything you do is just masking a problem that is already there. If she only cribs in a stall then maybe something about being in that stall is upsetting her - can she see or hear something that might be stressful to a horse? Or maybe she simply dislikes being stalled, or associates it with stressful experiences from her past. Could you not give her more turnout time? I'd be inclined only to stall a horse when necessary.
If all else fails and she's simply addicted to the habit, there are anti windsucking collars you can buy, but I'm clueless as to whether or not they're effective.
Oh, and just remember (because I know a lot of owners of horses with vices get trouble about this) vices are not copied by one horse from another - a horse cannot 'catch' a vice from being in the same barn as a horse who has it. Vices are a product of the horse's environment, whether they go away when that environment doe sor not.