Amazon gives you a good enough window into how someone rates items to know if they're pushovers or not. I know, because I've looked through several people's profiles when they rated things I had also rated. Odds are, you were right, and the person in question was too generous in giving out 4 or 5 star reviews. I understand it was difficult to find the one-star review, in the field of reviews she did, but then again, it wasn't really necessary. After the first page or so, you got the idea.
Rating is a very personal thing, and stars are subjective. I've read 4-star reviews that seemed overly-harsh for such a positive rating, and I've read 1-star reviews that praised items to high heaven, but came down on one point, and based the entire rating on that.
The subjectivity of reviews and the star system is why I think Amazon should do away with the stars altogether. I think a more useful system would be something like YouTube has: Thumbs up or down. You could then give the book an overall ranking on how many thumbs up vs. thumbs down it got. That would give buyers a quick view.
But the larger problem is, people shouldn't be looking for the quick view. The important part of an Amazon review is the text, not the stars. The stars are important because they allow some kind of overall measure of what people thought of the book, but the real meat is the text, without which you don't know what the rating means.