Just a personal observation.
As some of you know my senior Maxine has cancer, osteosarcoma and we are not treating her. She is doing "ok" so far, she is on tramadol.
Since Teddi joined our family 2+ years ago, she has been glued to Max's side. We call her "mini me" she worships the ground Max walks on. As a pup, Max was not happy with her arrival, and made sure that Teddi knew her place. However once Teddi learned to respect Max, they became best of friends, and actually were the two dogs who would play most often. Belle never seemed to have an interest in Teddi. She didn't not like her, she just never seemed to interact with her.
Recently I noticed Belle is less likely to sleep on the couch while we watch TV, she seems to be wanting to be nearer to Max. Even at night she tries to sleep near her. Then this weekend for the first time, I saw her actually instigate play with Teddi. More than once. Could it be Belle understands Max's situation, and while wanting to "protect" Max, also understands the bond Teddi and Max have and wants to let Teddi know she is there for her too?
I do think the dogs know what is up with Max, probably better than I do. DH and I have concerns over how this will effect Teddi as they are close. I was completely amazed at what I saw this weekend. Coincidence or real? Who knows.