If a mother kills five of her kids, but leaves one alive, I’d want to see if maybe that 6th child was fathered by a different male. She would have likely killed her other children to hurt their father.
My take is this, she had the 11 yo when she was 16, from her first love, all the other kids were from one night stands, she had no connections with their fathers. She figured her life was worthless but wanted her first born to survive.
An 11-year-old is more likely to comprehend what’s going on and maneuver/escape than the 1, 2, 3 and 8 year old children were able to.
Apparently she had issues keeping her legs closed