You said she took the MSF class, then said she took the dirt bike class.
Did she take the standard MSF class? Sounds like she had a temporary lapse of memory and forgot the "slow, look, press and roll" technique. It happens with more than a few riders. Suddenly braking hard and turning sure didn't help matters any.
This is pounded into the students head during class. Braking in corners=not good. Before I get some idiot arguing that is BS, remember, we're talking beginner riders, not advanced/expert technique.
If she still has her MSF class book, she should re-read the book...and maybe enroll in another class...and not follow you so closely(or at all) if you're going to be making sudden moves.
Riding a motorcycle requires 120% of your attention. Having the slightest distraction, be it on the road(not watching where you're going) or in your head(daydreaming) can be disastrous/deadly.
IMO its best to let the less experienced rider lead so they can go at THEIR pace and not trying to keep up with the faster rider(s)...which for some reason a lot of new riders try to do.