The Ballad And The Source by Rosamond Lehmann

Ten-year-old Rebecca is living in the country with her family when Sibyl Jardine, an enigmatic and powerful old woman, returns to her property in the neighborhood. The two families, once linked in the past, meet again, with the result that Rebecca becomes drawn into the strange complications of the old lady's life--with her husband, her errant daughter, and her grandchildren. Through the spellbound eyes of the young Rebecca we enter into an intricate and scandalous family history and slowly the story of the passionate, stormy life of Mrs. Jardine unfolds