The only thing my Bonies have acted mean toward are the gnomes. They go over to them, have even hunted them up, and kick them. When I had Pets they would play with the strays and teach them tricks. Let a couple into the yard. I have uninstalled Pets, so that problem no more, but still with the pick up the baby, put it down, pick it up again, put it down, walk away, come back and repeat this over and over.
The most frustrating thing I had with it was the baby would cry because Boney had woke it up. Mom or Dad would go to the baby but she would get there ahead of them. Most of the time they would stand there and wait until she put the baby down and finally left. If they arrived at the same time, the parent would step aside and let Boney get the baby. She would put the baby down, leave the parent would follow the order to pick up the baby, put it back into the crib leave and Boney would go back in.
By then it is close to morning and I have exhausted parents with one who needs to go to work and the other is so tired they can't take care of the baby as they are always wanting to go to bed.
Lock her up and when the baby ages to toddler let her out; hire a maid or just have my sim do the cleaning.