How would that go over if the provider refused the child to come tomorrow morning? Is it really worth the argument and potential on-going dispute of upholding the contract? Why is she leaving? Is there potential of this person spreading bad word of mouth to others? Even if the provider is wanting to stand her ground...Is it worth it?
Going forward I'd recommend she change that in her contract. Make it two weeks as that is more feesable for someone to pay as a deposit.
I, personally don't require a deposit, but all of my parents pay 2 weeks in advance, on Fridays.