The Magnificent Spinster by May Sarton PB

The "magnificent spinster" is Jane Reid, a teacher who became not only a revered role model but a dear friend to Cam, the narrator of this novel within a novel. After Jane's death, the accidental discovery of poems written by Cam in her youth to Jane prompts a flood of recollections--and frees Cam to imagine in fiction Jane's passionately vibrant life.