Sorry, you're wrong. She's the parent of the child and must assume responsibility for that child until it comes of age.
It's hard being a parent.
Whoever told you otherwise was lying. Perhaps you should have checked into this before you decided to have a child. An when you fail to hold up that responsibility, you should bear the consequences. Far too often parents duck the responsibility of their children. That needs to stop, as does passing off the responsibility for any of your actions. The fact is, you were not watching your child and that action caused the death of a very expensive animal. I think you should pay for getting a replacement.
Maybe the kid was trying to say he’d rather live with the gorilla?
"I absolutely adore you "I'm not judging because I wasn't there" people. You absolve yourself of the responsibility of passing judgement because you somehow believe it is the compassionate or right thing to do, when in reality you are enabling irresponsibility by your lack of courage to make a moral determination using your own powers of reason and ration."