December? I think that's plenty of time to learn to drive a stick. Certainly it would be a great deal easier for her to borrow/rent a car with a manual tranny between now and then than hope to learn how to shift on a race car. And I wonder if the instructors will even allow someone unfamiliar with shifting to drive themselves. As pointed out above, these cars are more tricky than your usual street car. I'm not sure, but do they even have synchronous gears? For all I know, they teach you heel-toe shifting, which I wouldn't wish on anyone who's never used a clutch before - that would be a nightmare.
Just this past weekend I took an open-wheel, formula race car course at the Bridgestone Racing Academy outside Toronto. They have a similar statement of what's expected of their students - driver's licence and proficiency with standard transmission. During the class the instructor checked that we all met those requirements, and then related a story of a recent student who showed up never having shifted in his life. Not only was he not allowed in the car, the intstructor was clearly exasperated that he even came expecting to drive such a demanding car with no experience.
Just words for thought. I'm considering the Petty course when my wife and I are down in Orlando in December, and I sure wouldn't want to go in there cold ...