I do not know if it is the way the story is written or not, but this mother not only sounds premeditated but also manipulative as well. A knife and bleach were found next to her person, but she was on the phone still when the police arrived. No real attempt at suicide was made on her part beyond a mere few tears. A suicide note redirecting responsibility to social services. No substantive and meaningful admission of guild on her part.
This smack of something other that just a mother freaking out or some time of "mercy" killing. Of course this is all conjecture, but I find most times society will go out of their way to not blame parents for their actions.
A voice from the wilderness perhaps, but an opinion nonetheless.
_________________
I don't have one.