wow, Arathi, I'm glad to hear that she started some communication with your son and she also relayed that she loved you and your son. That's something to be grateful for!
It sounds like you need to give her some space and when the time is right she'll approach you. Gosh, that's harder said than done. Easy to say, hard to do. If you are continually trying to see/talk to her then maybe she is not getting what she needs is that space and time to figure things out. In the meantime, you've got to prepare for the best and the worst and potentially something in between as there is no definitive outcome.
I definitely would be grateful she had that conversation with your son. I'm sure he's a bit confused and concerned by all this as well. Children sense when we are unhappy and worried and with this type of situation it's near impossible for me to show it. Reassure him alot that you are not going to leave him. Tell him as his age will allow the down right facts about depression at a level he can understand. Let him know that you can get help, it's like any other medical condition. My son was 24 when I became depressed, it took him a while to understand, he was in law school at the time.
More opinion, glad you looked at the session on grief, it works better if you work it - not criticizing, just commenting. And remember to be grateful for what you do have.....food, shelter clothes, your son, his mother communicating with him, etc.
Keep posting, we'll keep reading!