To stop me from running.
It's quicker, working, and less money.
Most likely because of money fraud, and she knew the secret.
Starvation, revenge, and human meat tastes nice.
I know families that would do that. They think it's unfair to the child and will go to any point to stop it, even murder.
So that it's harder to see blood stains, it's easier to hide on, and other stuff.