She graduated from Horace Mann School in New York and graduated summa cum laude from Yale University in 1987. She attended Yale Law School for one year.
She began publishing literary reviews in the Village Voice in 1990. Since then, her reviews have appeared in The Guardian, the New York Times Book Review, The New Republic, The Yale Review, and the London Review of Books. She has worked as an assistant to the literary editor at The Village Voice and as a tutor at Yale University.
Mendelsohn is married and lives in New York with her husband, producer Nick Davis, and two daughters.