THIS IS NOT LEGAL ADVICE, I AM NOT A LAWYER, DO NOT IMITATE MY HYPOTHETICAL RESPONSE TO THE HYPOTHETICAL SCENARIO UNDER ANY CIRCUMSTANCES.
If the seller or auto dealer does not have any permanent location for sale, and therefore, the sale of the vehicle took place at "[mama's] home, workplace, or dormitory, or at a seller’s temporary location, like a hotel or motel room, convention center, fairground, or restaurant; [and] also, if [mama] invite[d the] salesperson to make a presentation in [her] home" the Federal Trade Commission's rule of a 3-day "cool-off" period applied regardless of the absence of any statute-mandated "cool-off" period in Florida. Which means, she should be able to rescind the vehicle and/or the contract for the sale of the vehicle for 71 hours and 59 minutes of the time of purchase. (In California sellers typically print the hour and minute by which recision must be carried out.)
In civil cases, the burden of proof is generally not as high as in criminal matters, for example, in California, a civil suite for damages is typically decided by "clear and convincing evidence" as opposed to the higher bar of "beyond reasonable doubt". Some states might even apply a borden of the "preponderance of the evidence" which is even lower.
Therefore, even if she would not able to obtain any direct evidence, a witness who heard the misrepresentations, other forms of evidence may be sufficient to corroborate a written declaration under oath.
Some of these may include an iPhone's or computers logs which can be very, very detailed to the extent we are not aware, and be accessed by a layman after a few Google searches which may indicate that a certain website was visited, that it was visited at a certain time; phone calls if alleged that a great deal was conveyed to a family member or friend; text or email messages showing that mama found a deal and is heading to buy it or voice mail messages on others' phones.
If the devices themselves don't include such corroborating evidence therein, it may be helpful to reach out to the internet provide or telephone carrier if there was, in fact, a web search for the model actually desired.
It is important to gather all evidence, direct, corroborating or otherwise, and get screenshots of everything.
Other than that — and here goes my imagination...
If I was son I would try to call the dealership to see if their calls are always prompted for audio recording. If they always are and announcing and obtaining therein consent to audio recordings of their calls, that should also give mama the right to call and record.
If the calls are, in fact, consensually recorded of the dealership, I would help mama to record the call while she calls the dealer to explain how did this happen; however, if they are not, I would NOT try to record any calls because Florida is strictly all-party consent state for the purposes of recording, and it is illegal to record anyone without their consent.
If I would be consented to recording, I would not scare them, they may then refused to speak. If I was in mama's shoes, I would politely demonstrate the substantially similar naivety that resulted in the purchase in the first place. If they spoke up, that's great from there, it should be pretty straight forward.
I would also then review the contract. Florida should allow for although not proscribe a "cool-off period", that is, a couple of days when mama can “cool off” after all the heating the dealer would have given to mama's brain, and let her backpedal and out of the contract by recession.
Since, most likely, the "cool-off" provision would be a matter of discretion of the seller or dealer to have put it in the contract in the first place, it is fairly possible that it would not be there for mama to exercise. But, it would not be unreasonable to double check, dealers can get really, really sophisticated about the schemes they run: They may opt to put some fine prints so that they can convince the judge of no malfeasance arguing that if they would have wanted to defraud someone, why would they have put that there!?
Well, because you were expecting mama to be a complete idiot to never even notice, and it is always good to think of the what-if's, for e.g., what if mama notices, then we will argue as outlined above, and of course refund mama or do what it takes. If she doesn't notice, well, we just made bank.
If there was such a "cool-off" provision of the contract, I'd take mama back with that fraud of a car, and declared recision under the "cool-off" clause, and get the money back ASAP. If mama's bank was involved, I'd prepare all evidence, including the potential audio recording, to share with the bank, and would get them acting too, for e.g. as a matter of wire fraud or similar. (Good to remind myself that it’s much a matter of chance who we end up talking at the bank; one may have a stricter reading of their own policies when to act, one may have a less strict reading of it and will start the escalation — if I was to be rejected, I’d still try again, and maybe again learning from the conversations.)
If and when the money was refunded and retrieved, I'd still reach out to the police for the sake of it, and gave them all the evidence present at the time.
But of course, all of this is my wild imagination, and what I were to actually do is go get a lawyer for my mother, of course.