I'm so sorry, OP. As someone who has contemplated this for many years, all I can say is: Please, just be there. It sounds so meaningless and cliche, I know, but she is in an unimaginable amount of pain right now - so much pain that she actually wanted to leave you and her little boy. And now having failed at taking her life she will be faced with what she has done, on top of everything she was already feeling.
Just be there for her. I'm so, so sorry.