Outsidedave and anonymous44 posted good points.
One of the mistakes grandparents make is showing their priority is their grandchildren, bypassing the generation in the middle (the parents of the grandchild)
You have had excellent access and relationship to your daughter and her child. 3 hours every 2 weeks is excellent.
What do you mean by this?
"During the last 5 years I often felt that it was hard to make appointments with her."
I see an orange flag there.
To go through chemo therapy or choose not to?