Presumably the author means elves are incapable of evil. If so, she really ought to reread the Silmarillion. Lots of elves do evil things in it.
Probably one of the most unfortunate things about the current Rings phenomenon is the multiude of ignorant critics who first rushed to bash it (prior to and during the early run of the first film) and are now falling all over themselves to praise it (now that two wildly successful films ahve been released). It seems that most have read them primarily to check off the plot points as they appear-- or don't-- in the movies. I've yet to read a critique of the series that begins, "I enjoyed (or hated) the movies, but when I finally read the books..."