If you're the type of person that finishes every book you start, and you review most, if not all the books you read, then you're bound to have a higher percentage of books that you dislike or even hate than people who give up on a book after a certain amount of pages. For the woman cited in the OP, it's not as if every book she reads is given a 1-2 star rating. The majority of the books she reviews still have a three star or higher rating. So I don't get how she is reading to hate.
Are all the books she reads suppose to have glowing reviews?
I like chick lit. So I decided to see how many chick lit books I had given a low rating to. It turns out that I've 39% of chick lit I've read a 1 or 2 star rating. This doesn't mean I don't like books in that genre though. Maybe it's a high number because I've read more of those books and hence I've had a better chance of encountering books in this genre that grind my gears for whatever reason.