My sister has a nearly one year old Papillon, and an older Golden Retriever. The Retriever is your stereotypical loving friendly dog, not aggressive in the slightest. However the Papillon is quite possessive/territorial and attacks the Retriever quite regularly, to the point where the Retriever is quite wary of her now. It has bit her on the jowls causing minor bleeding, and this sort of attacking is commonplace although she tries to break them up prior to it escalating to that point. The Papillon is extremely affectionate and loving to the human family but does not like any other animals or people. My sister understandably loves this little Papillon to death and feels like rehoming is not fair to her, and also feels like there would be a lot of stigma to giving her up, like she's a failure. She did a lot of socialising with her as a puppy (classes, lots of outings and positive experiences, etc), but it seems as she's gotten older, she's gotten worse. My sister does not feel like she is capable of training this situation as she feels she's done everything "right", yet the Papillon is still like this. For example, my sister was in the front garden and a delivery man came by. The Papillon was out and chased the poor delivery man to the gate, snapping at his heels. This had never happened before so my sister was understandably shaken. I told her I would get some advice here, as there is so much collective wisdom! Would it be better for her to find this young Papillon a new home with a breed specific rescue group?