Leavel attended Needham B. Broughton High School and Meredith College, earning a degree in social work.

[7] She played the starring role of Beatrice Stockwell in The Drowsy Chaperone, for which she helped to create the character's backstory and which she referred to as "a compilation of a lot of different women in theatre.

Leavel succeeded Andrea Martin as Frau Blucher in the Broadway production of Young Frankenstein on July 15, 2008, and remained with the show until it closed on January 4, 2009.

[citation needed] She starred as Donna Sheridan in the Broadway production of Mamma Mia!, succeeding Carolee Carmello in the role on September 22, 2009, and leaving the show on October 10, 2010.

[21] Before the musical opened on Broadway (in March 2015) she was replaced by Heidi Blickenstaff because "the writers decided that the character needed to be younger so she could become pregnant, a key plot point.

[25] Manhattan Theatre Club has announced she will join Bernadette Peters and Lea Salonga in the upcoming Broadway mounting of the Stephen Sondheim musical celebration Old Friends.