I'm inclined to agree with the overall assessment that Graham is just not sure of Cassie. My question would be, how long ago did Graham's bud die? He may still be mourning. However, I believe in time you will see him react to Cassie. It may seem cranky at first as she gets on his nerves, but it will turn into real play later on. Ignoring behavior is one of the tricks I used to teach my students and dogs. If they are doing something like jumping up on me, I dress in old clothes and totally let them have at it until they get on the floor again. Then I give a "sit" command and praise and pet. I taught one dog that if my hands were behind my back, if she wanted any attention she had to sit and then would love all over her. She turned into a literal whacko and when she seriously bit my hand (thinking it was one of the other dogs, I think), she went to the Rainbow Bridge to learn better manners. She was a Flat-coated retreiver type (didn't know the parentage) and a good dog for the most part, but she did want to dominate the pack. Well, she's gone now, but I taught her by ignoring unwanted behavior and I bet that's what Graham is doing. Sometimes no response is better than anything to stop a behavior.