Inheriting Edith, by Zoe Fishman

From the back cover:

For years Maggie Sheets has been an invisible hand in the glittering homes of wealthy New York City clients, scrubbing, dusting, mopping and doing all she can to keep her head above water as a single mother. Everything changes when a former employer dies, leaving Maggie a staggering inheritance: a house in Sag Harbor. The catch? It comes with an inhabitant: the deceased’s eighty-two-year-old mother, Edith.

Edith has Alzheimer’s—or so the doctors tell her—but she remembers exactly how her daughter, Liza, could light up a room or bring dark clouds in her wake. And now Liza’s gone, by her own hand, and Edith has been left—like a chaise or strand of pearls—to a poorly dressed young woman with a toddler in tow.

Maggie and Edith are both certain this arrangement will be an utter disaster. But as summer days wane, a tenuous bond forms and Edith, who feels the urgency of her diagnosis, shares a secret that she’s held close for five decades, launching Maggie on a mission that might just lead them each to what they are looking for.