mistake over fridge could cost sale

[Tim Lindstrom]

I have a friend that sold her house.  During the final walk through, the buyers noticed the fridge was missing.  My friend always intended to take the fridge, and didn't list it on the included appliances,  but the contract has a stipulation that all appliances would stay (she didn't notice that).

She offered the buyers a concession of the cost to replace the fridge,  but they want her to put the original fridge back.

She is thinking of just putting the house back on market.  Can she do this?  What would you do?