Zuma has been really clingy after Classic passed as well. I don't know if I just never noticed it before or if it's a coincidence, but yes, I've been calling her my tumor-dog lately.
Years ago when my English Cocker Darth passed on my other spaniel at the time (Patton) was pretty much floored by the loss of his brother. It was sad and heartbreaking. It took a lot of love to bring him back to himself.
Yes, Teagan has always been with another dog, I think she might just be lonely without another dog, and I am sure she misses Mitsu. My poor Teag, Teag.