My insecure, fearful, follower of her alpha-dog sister seemed to know that her diva self needed to be put on hold when her sister got sick. She was a real trooper for a year and a half right to the end; way beyond what I expected. After a period of mourning, she is back to being mamma's girl - my funny, demanding, sweet, fearful, not-as-secure-as-I-would-like girlie-girl.
The important thing is to satisfy the things that are key to the non-sick dog, be it food, belly rubs, treats, walks, play, etc. It doesn't have to be "equal", just satisfying.