It almost sounds like mom and dad are not on the same page. Dad is saying enough is enough and attempting to discipline the child more. But if mom isn't going to then she will find a new way to manipulate. At the same time once you know the parents are taking a hard line then you can do the same and make her life miserable if she doesn't behave. And of course as others have said one more infraction and that is is no more two week notice.

Downside is if you give no notice it also doesn't give you two weeks of pay while you fill the space so taking the no more chances route actually hurts you as much if not more than them.