Maclean was born Heather Beach on October 18, 1972 in St. Louis, Missouri. She graduated from Cor Jesu Academy in St. Louis in 1990. In 1994, she graduated from Princeton University with a Bachelor of Arts degree in English Literature.
At Princeton, she was the Publisher of Business Today, the largest student-run magazine in the world, founded by Steve Forbes in 1968. While in college, she was an intern at Entertainment Weekly magazine.