Craig Shearman , Jun 07, 2012; 11:15 a.m.
No. You have turned down paying work and have no guarantee that another job will come up on that date. If properly described in your contract, the money she paid you is a retainer, not a deposit. A deposit is a down payment on a service and it can be argued that it should be returned if the service was never provided (I'm not a lawyer, so I will defer to those who are). But a retainer is a fee someone pays for you to guarantee to hold the date open. By turning down other jobs on that date, you have already provided the service.