Car Dealership Shenanigans

On Friday my sister visited a chevy dealership in Missouri. She wanted to purchase a new Traverse, but the dealership didn’t have the color she wanted. They said one was on a train on the way there and would arrive in the next week or two, and offered her a loaner car to drive until it arrived. She agreed, signed papers purchasing the car, even paid a $2000 deposit.

Today she gets a call from the dealership saying that the train company is refusing to deliver the car, they have no idea when the issue would be resolved, and that she can’t have the loaner long enough to find out. They’re attempting to pressure her into purchasing a different car, even though she already signed all the paperwork for the other car.

What obligations does the dealership have after money has been transferred and papers signed? They ran her credit on Friday to determine her monthly payments, but never got the car loan yet. So they haven’t been paid the full price of the car, just the $2000 deposit.

Are they required, by law, to deliver the original car? Are they required to allow her to continue using the loaner vehicle until her new car arrives, since it was a verbal condition of the purchase agreement? Should my sister get a lawyer involved, or is GM too big of a whale to sue?

Thanks for any advice.