I agree that the deposit is yours too, I also agree that trial days totally confuse a child and in my honest opinion the only person they benefit is the mom. I'm a cold turkey girl too and have only ever had ONE child in all my years not adjust (and to be honest I believe its because they attachment parent at home and I don't do that here)

I would explain to the mom that the reason we take holding fees and deposits is for this exact situation. You now have to advertise, interview and will lose the income for Jan because she pulled at the last minute. I think you dodged a bullet with her. It was only a matter of time before Gramma became the daycare provider!