This is going to be hard to prove.
You can complain about them to the Department of Consumer Affairs in your state but as there was no one checking and a new contract was signed and she took delivery it is deemed that she accepted it as it was.
The manufacture date is an issue for the dealer.
If they said and advertised it was a 2015 manufactured car and they sold you a 2014 car then it is misleading and deceptive conduct.
This also has to be in the contract. The salesman will deny anything that is not in writing and it is your word against his and difficult to win. The courts prefer documentation.
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