Just as you were no doubt upset about the loss of your dog, so is your other dog. In fact, given that the surviving dog had a constant companion in the other dog, it's understandable that she may even appear more upset. However, with time and lots of love and attention, she should get better. What she may be missing more than anything is that companionship. You can, of course, get another dog and that would likely help. If you're hesitant to do so, though, there are other things that you can do. Set up some play time with other dogs or even take her to a doggie day camp or day care center. Try to add a little bit of what she's missing, namely that canine companionship.