In my view colleges tend to assign way too much reading to students. In fact, colleges have essentially become reading and lecture factories, with little hands-on learning available to undergrads. This is great for professors, who tend to leave the "teaching" to teaching assistants while the profs focus on research and activities that further their own educations and careers within academia.
The main reason students and their parents pay exorbitant sums for this kind of education is because a degree is generally required to enter the workforce. The quality of the underlying "education" isn't normally questioned, just the ranking of the university and the work opportunities offered their graduates.
Joseph Campbell left academia when, in his attempts to obtain a graduate degree, his own interests began to be channeled to match the interests and needs of the schools and professors. Since this was occuring during the Great Depression of the 1920s, there were precious few jobs available and higher education was expensive compared to the average wage (much like it is today...).
So Campbell decided to take five years and persue his own educational/reading interests while living cheaply in a cabin. After this period he landed a job at Sarah Lawrence College, where he taught for over thirty years. As far as I know Campbell never obtained a degree higher than a bachelor's and yet he had a distinguished academic and writing career.
In my opnion there is no higher education available in the U.S. today that is worth its cost, particularly the indebtedness and lack of personal freedom/choice that it requires of our young people.
If you want to kill your granddaughter's love of reading, and presumably learning, I can see no better way to do it than signing her up for a speed-reading course or trying to channel her natural, self-directed inquisitiveness to more closely match those qualities valued by our educational system.