I actually think this kind of killing is very rare with women. I also don't think the cases cited above evidence an increase of killings by women. We have always had women who kill children in their care or their own kids, etc., either to get rid of the "burden", due to mental illness and enmeshment issues or abuse gone "too far". But this kind of crime, a woman killing a child they really don't know, that's a completely different animal. In fact, except for murders related to sex crimes, or some other sort of serial killing, the intentional killing of a child not related or affiliated in any real way by the killer is extremely rare, I think, by people of either sex.
However, there does seem to be somewhat of an increase in overall aggression in women in recent decades. "Girl fights" on youtube, women beating up or murdering romantic rivals, etc. I think our culture values violence overall, more and more and it's horrible.
Regardless, this crime is incomprehensible. Why any person would kill a little child, not their own, perhaps due to a robbery interrupted, or a drug debt or revenge or whatever, is sick and beyond comprehension. This person has no soul.
