Martha Stewart was bit in the face - several stitches!

Martha Stewart was bit right in the face by her own dog - and required several stitches! What caused the dog be so vicious and attack her owner? Why did Martha call the police for a ride when her own driver was waiting outside? Full story at http://news.yahoo.com/s/ap/20110114/ap_on_en_ot/us_people_martha_stewart_2