Looking at it from my point of view, every time that someone puts something on twitter with my hashtag, it goes out to everyone on their twitter lists. If any of those people go, "Who's Azazel?" that gets more people to (possibly) look at my book. So, obviously, I want people to tweet that hashtag as much as they possibly can. Allowing people to vote more than once keeps people putting that hashtag out there.
So, um, I kind of dig the "spamming." What it says to me is that this contest is important to her and that she doesn't mind promoting my book on her twitter.
Thanks for your input, though.