She's just far enough along on the Hot axis to tolerate a little "extra credit" activity if you're in her class.
After all, college is supposed to be 'work.'
Back around 1972 I had an Economics prof who was perhaps 30, really quite hot, and per the style of the day, wore very short skirts. She also liked reaching up to the top of the blackboard (remember blackboards?).
Staying awake in Econ 101 would have been difficult were it not for the suspense.
We all worked hard in that class.