The L Shaped Room by Lynne Reid Banks

While the main plot centers on a heterosexual woman (Jane) who gets pregnant after a one-night stand, the book features a prominent, positive secondary lesbian character named Mavis. Mavis is a professional jazz musician who also lives in the boarding house, and she acts as a deeply supportive friend, protector, and mentor to Jane. For a 1960 novel, Mavis is portrayed with unusual dignity, warmth, and respect rather than as a tragic or predatory stereotype.