Hi Thundarr,
I'm no expert, just another LBS trying to make sense of this confusion. My H is one of the few people who has managed to express what he is going through, and this gives me some advantage in understanding all this. Not everyone gets the chance to listen to their MLCer, but if you can, do. Listen, don't judge, just validate, and don't take it personally.
In your W's case, from what you say, it doesn't sound like it was triggered by stress, she doesn't seem psychotic, but perhaps her mother's Alzheimers has made her fear for what she hasn't achieved. Instead of facing her loss, she's turning backwards and regressing. It sounds like she's trying to escape her reality and live/ re-live her youth (like so many MLCers).
In Jungian psychology, ML is a time of transition, of embracing the shadow self (the repressed/ unacknowledged side of one's psyche). But this isn't conscious, and in crisis there's just a feeling of a life that they haven't lived, and being trapped in the life they've made. I feel that my H has built up a strong disassociation with his right hemisphere, and has forgotten how to be happy. His left hemisphere, critical, controlling and analytical, may have been damaged through stress burnout.
In the case of your wife, I don't know what could have led her to the point of crisis rather than transition. Did she grow up too quickly? Did she miss out on part of her adolescent development? Or were her home and family routines overwhelming?
It doesn't hurt to send some truth spears about the effect of her behaviour on your children (but keep them light and sharp).
I don't know her or if I will ever see her again. I know I may never trust her or anyone else again as I fear I will have this constant fear that they will turn against me suddenly for no discernible reason.
I know how painful this is. You have a long journey ahead. I have the feeling that we were as trusting as children with our spouses, and never expected this behaviour. Slowly, we have to regain a sense of ourselves as whole, wonderful people in our own right. We're not half of a couple. We have to take responsibility for our lives, for our pain, for our future. WE have to lovingly detach ourselves from what our spouse is doing. It helps to understand, but we're not responsible for them, only for ourselves, and our own feelings.
Eventually, if and when your wife sees this new you, it will change how she sees you. Then, you will be strong enough to decide what and who you want in your future.
Take care, Mermaid.