Where is the property, and what age is your daughter? I need to find the appropriate legislation, and your daughter may not be of full legal capacity. If she is aged 18 or less, the contract may be voidable.
Even if it is though, what alternatives does your daughter have? If she likes all other aspects of the property she may find that the terms of the agreement are common (even if they may not be legally enforceable). So what alternatives does she have?
If she genuinely does not want to rent this property, then my advice ,(and ONLY if it's true that the letting agents could easily let it to someone else), would be to breach the contract by not moving in and not paying any rent.
The letting agents could sue your daughter and;
1. Force her to meet her contractual obligations.
2. Rescind the contract.
3. Look for damages.
But, oprtions 1&2 don't look so appealing (if I was the letting agent). Why go to the bother of fighting your daughter through the courts when I can easily let it to someone else? And why rescind (terminate) a contract when it's clearly not what I want to do and is not in my interests?
Option 3 looks good to the letting agent! But to get damages the letting agent would have to show loss. If they re-let the property easily within a short space of time, what have they lost? Very little - so your daughter would be liable to pay very little. If they re-let it for less than your daughter agreed to rent it for though, your daughter would also be liable for the difference.
So, depending on some questions you need to answer for me, the contract may not be enforceable at all. But if it is, it would seem that non-performance is your daughter's best strategy. I don't see any value in the letting agents taking the matter further if they have little to lose. It will be less hassle to accept the breach rather than pursue the matter through