Such a sad story, and such a failure to protect those children. I can only imagine the desperate situation that mother found herself in.
I have extensive experience with mental illness, personally and professionally, and it is something that can be difficult to understand if you have never experienced it. Tragically sometimes mental illness is a terminal disease, even more tragically it is sometimes fatal for people around the mentally ill. The resources and facilities available for mental illness in Australia are a disgrace, and are not even adequate to deal with the most desperate, most serious cases let alone prevention and support.
Please, if you are ever in need if help, find that one person in your life who can be your advocate (partner, mother etc) and tell them everything. They will need to fight for you, and sometimes it is just too late, and too hard for you to do all the fighting for what you need yourself.