I assume that by not bonding, they mean not bonding to anyone. Unbonded children are basically sociopaths, so the theory says, and are without emotion, and pretty much will be institutionallized for the rest of thier lives. These children can be seem pretty normal much of the time. I have worked with children like this, and its pretty sad.
There are several controversial treatments available for this, and I would assume that most do not involve Killing your patient. Back in my psych hospital days, I heard good things about Foster Kline, but his methods are illegal in this state, so I never witnessed them(IIRC the involve having the parents hold the child down until the child totally freaks out, then picking up the child and consoleing them until they calm down. This some how made the child bond with the parent. A lot of the people in the psych world that I respected said it worked, but I really don’t know. THere was a made for TV movie about it many years back.
If she was an “unbonded child”, I can understand the mothers desperation, but nothing excuses what they did.
Really a sad case anyway you look at it.