Yes, she is very horrible at dealing with her emotions. She still dwells on her friend dying almost 9yrs ago or so. I can't tell you how many times I've tried to get her to talk about it to ease her pain. All attempts failed and I just got to watch her suffer and try to do my best to comfort. She is a very lonely person and isolates herself all the time.
Well, I'd say you have your answer. This is the type of person you married. Sounds like other than her family, she doesn't trust other people. And, you are "other people." I dated someone like this. In the end, I felt the guy had a boatload of emotional baggage; certainly more than I wanted to take on.
You knew what you got when you married her. She sounds clinically depressed. JMO, but I would guess that her depression and inability to cope with what life throws her way, has a whole lot more to do with her leaving the marriage than you.
And I think that is what you have to examine. I don't think you are nearly as important to her as she is to you. If she got into some serious counseling and went to a doctor to find out if she needs medication, things might turn around.
The only problem is, people who don't want to be fixed will refuse all help. They would rather stew in their own pain, because that pain is familiar. Kinda sick? Yeah. But I married one like that. Which is why I no longer am living under the same roof. I couldn't fix him. He didn't want to be fixed. Our lives. Our choices.
You can try to reach out to her to see if she will get help. If she doesn't want it, you might want to explore your options, like going to counseling for yourself, seeing an attorney to get information ... just have your ducks in a row.
This is painful, I know. Life is full of pain. We all want to avoid it. Unfortunately, life comes 'round and slaps us in the face. You will get through this pain. But you have to go through it to get past it.