We thought that her seeing her own refection was the issue as well, so we did just that. We taped paper towels on the outside of the cage and she still did it. So we thought she could still see herself somehow so we put the paper towels on the inside, and it still happened. We have only had a problem with males seeing their reflection in the glass, so they went into a glass free, wooden rack system we built. Out of all of our females, she is the only one to ever get mad at "nothing" per say, and why NOW?
We have experience in females rejecting males or possible cage mates by flattening out and/or bobbing/blackening of the beard, but not to themselves before. Guess she will have to join the males in the wooden system then . . .