I will add that my D once took a 2 week 3 credit college course. It was a bit crazy --class started Monday, midterm Friday, final the following Friday – with 5 hours of observation, a demonstration, and a paper in between. The course took up virtually 100% of her time, energy, and attention for those two weeks. But even with the very compressed time-frame, she learned a ton and was so grateful to have the chance to take this class at a local college over the semester break as her college did not offer an equivalent course.
So bottom line is if your D decides to take a compressed class, she should be committed to giving it her full attention for the period of time the class in is progress.