Just put this down to one of the tragic people with mental illness. I remember reading of a crazy woman in Britain who preferred having abortions to using birth control. She had well over a dozen abortions, and tried to get pregnant just so she could abort again.
There really are few depths to which the mentally ill will not descend. Some women develop the “Medea syndrome”, in which they feel compelled to murder their children. If the children are still infants, this is often written off as “postpartum depression”, though the women show no signs of depression, just an intense desire to kill their children.
Often it is murder-suicide, most commonly done in a vehicle, when the mother just decides to drive off a cliff or into a lake.
There are a huge number of mental illnesses. This woman has one of them.
That's common.