@Blueberries, did the officer give any reason for not choosing the domestic helper route? They probably consider it a ridiculous choice, but I don't think there would be any reasons for rejecting your application.
I don't know if this is a route that you would want to go, but you could offer the girl to support her taking Chinese classes, getting a study visa, and then give her free lodging in return for occasionally looking after the kids. It of course would make you a criminal felon as people here will quickly point out, but it is a route others have taken.