My 12 year old Brittany Spaniel Meg suddenly sleeps alone downstairs - she doesn't seem to be in any pain, but she has been acting a bit strangely in the evenings. Some Background: In Dec 2015 her sister from the same litter suddenly died, leaving her alone. They had only ever been separated for half a day in their lives. We often left the two of them in the house alone while we were out at work and they seemed fine - we have a very large garden with a dog flap to the house, the full run of the house, a television left on, and a paddling pool left out in the shade during the summer. Cleo (the one who died) was the most dominant of the pair, and Meg has always been somewhat insecure, especially with food. Since Cleo died, Meg has been left alone in the house while we were out at work. While she seemed depressed for a few weeks, she started to perk up again over time. My mother was between jobs at the time so was able to give Meg company for a few weeks. About 6 months ago, we took on a Jack Russell called Gypsy from someone who couldn't care for him anymore. Gypsy is about 4 years old and very energetic. He loves playing tug-of-war games (especially with me since i very rarely let him win). Meg doesn't like him playing these games and often snaps or whines at him if its close by. I imagine this is because she knows the rules - anything she has that i want, i can take. She knows this and will allow me to take anything off her to the point where she never played tug-of-war games. Gypsy obviously doesn't get this yet, so she snaps at him. I also know how to handle Gypsy and will often pick him up and rub his belly, which he doesn't allow anyone else to do. He does play-bite my hands and i think i'm the only one in the house that doesn't flinch when he does. Meg is like a parent to Gypsy - constantly keeping an eye on him and correcting bad or over-energetic behavior. Gypsy will cower or lower his head if Meg is staring him down. Both Meg and Gypsy are left alone in the house while we're out at work, and the two of them seem very happy during the day. Meg has especially perked up, however during the evenings she tends to sleep alone downstairs while everyone else is upstairs which is very odd. Meg always slept on my bed or with my father but since Gypsy moved in, she rarely wants to. I don't know if this is just age and unwillingness to climb the stairs, if this is a territorial thing between her and Gypsy, or if she just wants the peace and quiet. As i said, she doesn't seem to be in any pain - she has had problems with her back legs all her life, although since shes been on medication it doesn't seem to be a problem for her. Its only started in the past month or two - it could just that its slightly cooler downstairs in this summer heat. Am i just being over-concerned or could there be an underlying problem here?