You shouldn't blame her. In fact, you should commend her ... for creating something that inspired millions of people (in particular children)
to read.
I realize I am being pedantic ... but statements like "for her success,
blame the masses for their taste" and "You can't
blame her for how much money people spend" miss the point that Rowling's success was instead a product of her effort, creativity, and productivity - that she actually
inspired people to spend money on
books despite a whole host of other options (movies, music, video games, etc.).
To put it another way, one statement places responsibility for Rowling's financial success on the fickle tastes of "the masses" while the other acknowledges that Rowling's own efforts effectively drove "the masses" toward a behavior that ultimate benefits all of society: increased literacy.
So yeah ... I think I get what you mean. Personally, I'd just frame it differently.