I have two dogs. Prissy is a yorkie--about 41/2 lbs. Prissy is a American Hairless terrier (a Rat terrier with no hair). Both are female....or so I thought. Prissy is in heat. We thought Pinky might be also. They have always been in heat together. Today I caught Pinky trying to mate with Prissy???? What is this? A dominance issue? Gender confusion? Prissy had been mated prior to coming to live with us. Pinky has not. We got her at 6 months. What do I do????