The Blue Castle

The Blue Castle by Lucy Maud Montgomery is a novel published in 1926.
Twenty-nine-year-old Valancy Stirling has spent her entire life suffocated by her controlling family's expectations. When she receives a shocking medical diagnosis, she decides to finally break free and live on her own terms. She scandalizes her relatives by speaking her mind, moving out, and eventually proposing marriage to the mysterious and supposedly disreputable Barney Snaith. Together they build a new life on a remote island—but secrets still linger.