I thought I heard a lot of people had trouble with this because they pressed the button too fast (which was causing it to measure incorrectly), you can press it at a fairly slow pace and have it work.
Vice Destroyer wrote:Also, don't make the mistake I made and use the Fire Axe to fight her. That is a terrible weapon for her. Use the pipe when she is in Spider form. Much, much easier. I know this now after about 3 hours of playing.