I've noticed how when someone commits a terrible crime there is a tendency to portray them as a monster and a demon, a "psychopath", to distance them from the rest of us, to cast them out from humanity in a reassuring way, and then look back for signs that should have been spotted sooner that this person was not one of us.
I remember a news report showing the class photograph of Harold Shipman at primary school and calling him, " a sinister child in a bow tie" in the gravelly voice used to describe baddies in film trailers. On this thread people are saying some people are born evil, the parents must have known etc. I always wonder of this is a coping mechanism for society, so that we feel less guilty for not noticing that people who ARE humans, who have friends, socialise etc can do these things.
The reverse seems to happen too: what was that case in Bristol where an older, eccentric single man was falsely accused of murder?
As she was an ill baby herself, had a traumatic birth and became a cosseted child, maybe yes there is a logic here: all those babies are now ill like her, and she can save them or her potential lover can save them, or she can see how devastated the families are. Subconsciously she might be reliving her own trauma, making it play out again and again. There can be logic there, without empathy to limit her actions. I don't imagine many people who commit these crimes are rubbing their hands together like a stereotypical villain.