Deposit held ransom as agent made dbl booking

We are meant to have a 9 am exit inspection with Lourentia tomorrow morning and because she has made a double booking she is threatening that if we do not meet her in her new proposed time slot of 2.30 which we cannot make as we are moving from the northern suburbs to the southern suburbs she will hold our deposit for pro rata rental and expenses the new tenant may incur due to not being able to take occupation. She confirmed the 9am appointment with us on Friday afternoon and has waited until Sunday to advise she has made a double booking. We have offered 4 alternative time options including coming through today but she has told us out-rite that it is her proposed time or nothing. How can this be ethical giving a tenant less than 24 working hours notice to change an outgoing inspection and then threatening to use the deposit to cover costs incurred because of what is ultimately her error??