The Royals never seem to visit their family when they are ill. I don't believe the Queen even visited her mother or sister towards the end either.
It's pretty poor, in my opinion, and doesn't reflect well on her, especially as she is on her Christmas break now. It's not as if she has to use that time, like most people, to rush around getting last minute shopping in, cooking it and clearing up afterwards but would still find the time to visit sick older members of the family! I can't see H and M rushing back either!