We had a couple of Shetlies years ago that were two peas in pod-- the were inseparable and where one was the other was just feet away. The male died suddenly when he was 11, he was diabetic. His BFF was a female and she was totally distraught- long story short we decided to get another dog to keep her and us company so we got a puppy. He was a bundle of energy, friendly, playful and ready to go all the time, the female would have none of it. He would come up and solicit play and she literally would turn her head away from him. Eventually she got to tolerate him and even played a bit with him but never ever really accepted him and it broke our hearts. She was 12 when the pup came into her life and I guess she had only one BFF in the whole world and he was gone. Within a year or so she died from a sudden onset of something we never found out what- maybe a broken heart. I never regretted getting the pup he was a great dog and after she passed we got him a new bud (we brought him to the breeder to meet the pup) it was love at first sight and they were great and became bffs -- they were 3 yrs apart.