What is the theme in The Shell Seekers by Rosamunde Pilcher?

The mother/child relationship is at the heart of this story. The Shell Seekers essentially explores this relationship between a mother and her children from both perspectives. For Penelope, it is distressing to watch her loving children become the adults they have chosen to become. Her daughter Olivia is the only one who really understands her and it is for this reason that she communicates closely with her, updating her when she returns from the hospital, when she takes a trip to Porthkerris with Antonia and Danus and when she gives Antonia the pearl earrings.