I have commented so many times on this issue as various cases have appeared on here.
These women claim to be mentally ill, (which I would say is true) and didn't know what they are doing at the time, and many times they manage to sucessfully kill their children. When it comes down to taking their own lives they just can't seem to do it. So if you kill your child in a rage of complete insanity how are you able to rationalise when it comes to taking your own life? They must think at some point, I really don't want to die. Maybe I am reading this all wrong and they try to kill themselves but fail and just end up badly injured. Wonder if there has been any studies on this. I may have a look, just out of curiosity.
BBM
If we assume mental illness/personality disorder (and I believe this is true in many of these cases), then when stress reaches a certain level it throws a person into "overdrive" or psychosis. I tend to think that if the stress of caring for a young child is the precipitating factor, once that child is "inanimate" or dead and no longer has needs to be met, the psychotic person has immediate relief from that stress. Its then just a matter of time, individual to that person, before they understand the reality of what they have done and can rationalize the consequences. Hence the suicide attempt.
So if the child killings happen during true psychosis and there is an interval before the killer attempts to kill themselves, they might only be in a depressive state by this time.
If they are personality disordered, they may also have never bonded with the child in the way that most of readers here identify with. They may have simply imitated what they understood to be acceptable parenting behavior, without the true, deep, heart connection.
Synopsis: 1) Child killings = madness, insanity, psychosis
2) Suicide attempt= darn, now that my worst problem is solved, I
have to off myself (but they don't really want to die)
That's just my-opinion-only-armchair-analysis. Not much has been said about this mother's family of origin or what kind of support she had in her life as a single young mother caring for twins. I wish we knew more.