I agree, it's pretty hard to miss all the SRT badges on the car, but one never knows....it could have been de-badged before she bought it. (I doubt they would have been removed from the seat covers though).
I'm assuming it's your typical XF Florida roadster, which should mean it's still in pretty good shape.
The biggest determining factor would be the mileage.
If they don't offer her more money, I'd tell them to find her a comparable Crossfire Convertible to replace hers.