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I am sorry to learn of your daughter's situation. Unfortunately, while there is a great deal of law concerning "security deposits" (getting the money back that you pay a landlord to cover damages or unpaid rent), there is very little that covers "holding deposits" (such as the money that your daughter paid to her landlord to reserve the house for her tenancy.
The courts generally disfavor "liquidated" damages (contractual damages that have no bearing to the actual damage suffered by the "injured" party). So while your daughter breached her contract with the landlord, it is unlikely that the landlord actually suffered financial damages that amounted to the entire amount of the deposit. They are likely relying on the unlikelihood of your daughter suing them in small claims court to recover any portion of her check.
What she can do is sue in small claims court for breach of contract. In this action, the landlord would be forced to prove their actual financial damages due to your daughter's backing out of the lease. (This may or may not amount to the entire amount of the check depending on how long it takes for them to lease the unit - but she can try this).
Short of filing a lawsuit, you can try to mediate the dispute with them - contact your local bar association and request referrals to mediators, a third party neutral can often help you reach a mutually agreeable resolution. Use the bar association's referrals to contact a mediator or two, the mediator will then contact the other party to set up a mediation session, and you can go from there - hopefully resulting in a formal or written settlement agreement, and save yourself the time and expense of litigation.