My first guess was boredem and even more so when you said she didnt do it when the farrier was there. If i recall correctly Maddie is an Aussie with HD so shes on a controled exercise plan? She needs stuff to do. Feed her out of kongs hide her kibble. Play mind games with her and make sure you cut down her food to the correct amount now that shes on the good stuff. I am not a huge spay fan if you are taking care of her and shes not in a place to get preggo but it is definetly something to think about if shes over 2 and shes done maturing