CL, I think that the less stress your W has in her life, the happier she will be. It sounds like she doesn't handle taking on too much responsibility too well. And I can understand that. When I get overwhelmed, I get angry and down. It's like too much is going on in my head and I don't know which way is up.
I, too, recently went part time. I used to work full time (because I had to -- or thought I did). Then I got laid off, which ended up being great for me. My company ended up hiring me back after about 6 months. But during that 6 months, I gathered myself and figured out what I needed to be at peace. And NOT working full time was one of those things. At the time, I was potentially headed for a D, but told myself I'd find a way to work part time and make ends meet.
My company ended up hiring me back part time. This has made a dramatic difference in my life. I am so much happier with my general lifestyle, which permiates to other areas of my life. Sure, I still get overwhelmed but the kids, and work, and life in general. But at least I have some balance now.
My point in turning this post onto my sitch, is that I can understand to some degree how your W gets into a bad place. So, I think it's a matter of adjusting your/her lifestyle to better meet her emotional well being (while ensuring your emotinoal well being is in tact).
Married 9 years Kids 5 and 6 Bomb 2006 H back and forth for a year M now back on track