I'm sorry this problem led to separation. Obviously, I can't say for sure what's happening (and I'm neither a doctor nor psychologist), but something like 10-15% of women go into deep depression after childbirth - postpartum depression. That's really no different from depression at any other time, and one symptom can be shutting down emotionally with the people closest to them.
This is an illness that can push someone into despair or rob them of all feeling.
There's another problem, though, that could be going on - bipolar disorder. That's characterized by mood swings, from deep depression to hyperactivity. It would take a consultation with a psychiatrist or at least a family doctor to diagnose what's happening.
When I was depressed, I often felt I could solve my unhappiness by leaving my wife. Fortunately, things didn't go that far, but I caused a lot of hurt for her.
If this is what's happening to your wife, her behavior toward you is part of her inner struggle. You take the brunt of it, but whatever she says - and abusive behavior is part of it - it's about her depression, not you.
I hope she can consult with someone soon to get a professional opinion on what might be going on.
My best to you -