I really like this show. I love Laura Linney. I think they've created an interesting scenario with this show.
I can understand why Cathy doesn't want to tell her family. Once she tells someone, she becomes "the woman who is dying" & she has to deal with their emotions (or lack thereof) in addition to her own. Sometimes, it's nice just to feel "normal".
We have someone in our family who is very ill. The person's spouse is exhausted & feels the caregiver gets no attention. The person who is ill tends to take too many chances & does things that are unhealthy in order to make the other people in the family feel normal. It's a weird myriad of guilt, fear, anger, sadness, exhaustion, optimism, pessimism, etc. It's never easy.
I thought the woman in Paul's office gave a poignant speech on her role as caretaker to her husband dying from cancer.