Why does the mom cat attack her kitten after was spayed?

Spaying a cat does not cause it to become aggressive towards its kittens. While it's possible that a cat might exhibit some temporary changes in behaviour shortly after surgery, such as feeling groggy or irritable, this should subside within a few days. If a mother cat is displaying aggression towards her kittens after being spayed, there may be an underlying medical issue or stress factor that needs to be addressed. It is important to take the cat to a veterinarian to rule out any medical causes of aggression.