The show has never been called "Amateur" Idol and, knowing how this industry works, would have been canceled years ago if it had. There's a reason the show is NOT amateur only: RATINGS.
All "reality" shows by nature are not, will never be, and can never be 100% fair. It can be argued that she comes into this with a small fan base, but it's a drop in the bucket compared to the millions of votes. Now people like you are judging Joanna very harshly--even before the show's really begun. So her past experience is a tremendous disadvantage for her if anything else. So whether you like it or not, Joanna meets the show's criteria and she deserves to be a part of it.