I don't know what that means. Every quantitative study done over the last decade which employed control groups has found that people in their middle-years are no more prone to having a crisis than people in any other age group.
I would suggest that day-to-day life stressors are more important. Bills, housework, relationship problems,jobs, child rearing, illnesses, grieving the loss of a loved one, and so on can alter a person's perspective. And then there's the possibility that the perspective was never optimal to begin with, and that combined with ordinary life stress and relationship issues just had a cumulative effect leading to a crisis.
You personally can't do anything to change her perspective, but you can change your own, and that has an impact in that it at least changes the dynamic between you two.
Enjoy the present, make reasonable plans for the near future that don't depend on your spouse complying with them, and when you think of the past, focus on the good things or the positive lessons learned.
Don't ruminate on the negative (which is mostly what I see going on in there).
A perspective high in past-negative or present-fatalistic (nothing I do matters) and weak in future-positive, past-positive and present hedonic (enjoying yourself and appreciating things) will lead you into misery and bad behavior patters.
M-47,W-40,No kids D-filed 5/27/2010 Piecing - 10/21/2010 -=Soon to be banned=-