No we didn't transfer title and she didn't take the car she just wants her 900.00back and that's fine with me but do I have to give it back before we sell the car I'm out 2500.00 because she changed her mind and no she didn't didn't sign anything
Well...I submit that anyone who is stupid enough to give you $900 without anything in writing and without having title transferred can be easily manipulated and duped.
That said, I suspect your verbal agreement did not include any sort of provision about what would happen if the buyer backed out of the transaction before taking possession of the vehicle or making any of the monthly payments. If I'm right, then the buyer is in breach of the contract. However,
your failure to obtain a written contract for the sale of goods in excess of $500 means the contract isn't likely enforceable. If the contract were enforceable, your remedy would be as described above by "adjusterjack."
If you don't give the money back, she may or may not sue you. Any lawsuit would probably be filed in small claims court, which should be quicker than regular court, but will probably still take at least a couple of months to go to trial. By that time, maybe you'll have sold the car to someone else.
By the way, your statement that you're "out 2500.00 because she changed her mind" is obvious nonsense. You have the car, you have the title,
and, until you return the buyer's down payment, you have $900 you didn't have before.
One more suggestion: don't sell or buy a car to/from a friend unless you want to ruin the friendship.