The youngest dog of the household has become increasingly aggressive and possessive in the past few months. It started with her harassing the other two dogs in the house when they were trying to eat or getting any attention at all. Today she tried to attack my dog for no apparent reason. She's about a year old, isn't fixed, just had her first heat a couple of weeks ago, and has known and played with the other dogs since she came from the breeder last summer.
Her owner does not discipline her beyond an 'aw, don't do that' and gets quite upset when other members of the household attempt to discipline her or talk to him about her.
What can be done to stop this behavior? Moving elsewhere is not an option.