Don't know if it's already been said, but some people get free ARC books, with the promise of an honest review. I can't say you'd still have a point in that, if she doesn't seem to like the genre, why take the freebies, but some people just can't so no to "free".
Or, she may feel she provides a service (at which point, I'm hoping she's young, because life really is too short to spend that much time doing something you don't like just "because") - by reviewing the drek, she's saving other poor readers from the mistake of purchasing those books!
