Shlesinger was born in Manhattan, New York, and was raised in Dallas, Texas. Her family is Jewish. She attended the private Greenhill School and participated in the school's improvisation team. She performed with ComedySportz Dallas and attended the University of Kansas for her freshman year. She also participated in Semester at Sea. She transferred to Emerson College in Boston, where she majored in film, refined her writing and editing skills, and became a member of one of the campus's comedy sketch groups, Jimmy's Traveling All Stars.