<human>: Can you give me a shortened version of the text?

So my friend has enough cash on hand to buy this car straight out.  The dealership was offering a student discount of $1000 if she financed for atleast 90 days.  Furthermore, the dealership allowed the buyer to make a choice between $750 off the retail price or a 1.9% finance rate.  Since my friend was just going to take the student discount (by financing) and pay the balance at the end of 90 days, she took the additional $750 since the finance fee wouldn't be affecting her too much over 90 days.  NOW the dealership has called, after the contract has been signed and my friend has driven three hours home with her new car, and is telling her that they weren't supposed to give her the student discount.  They are telling her that she will either have to pay an additional $1000 (to make up for the student discount) or return the car back to the dealership.  Is this legal?  Once a contract has been signed, is the dealership obligated to honor that contract?   Any help would be appreciated.  I can answer any questions about the contract as I have it on hand.
<bot>: Friend bought a car and signed a contract.  Now dealership wants more money than is written in the contract.  Is this legal?