Leavel attended Needham B. Broughton High School and Meredith College, earning a degree in social work. She completed a graduate theatre degree at the University of North Carolina at Greensboro in 1980. She acted during college, appearing in productions such as Cabaret and Hello, Dolly!

Her Broadway debut was in the 1980 production of 42nd Street as a replacement for Annie. Leavel was in the original Broadway cast of Crazy for You (1992) as Tess and an understudy for Polly Baker.

In 1999, she played Mabel and Mrs. Bixby in The Civil War. Leavel returned to the revival of 42nd Street in 2002 as a standby for Maggie Jones and Dorothy Brock, eventually playing the latter.

Leavel replaced 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.

In 2009, Leavel starred in a stage reading of Dylan Glatthorn’s Republic with Lauren Worsham and Kelli Barrett. She also starred in the staged reading of Vincent Crapelli’s Otherwise, with Karen Ziemba and Laura Bonarrigo-Koffman.

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

Following Elf, she appeared in the Broadway production of Baby It’s You!, which began previews on March 26, 2011, and closed on September 4, 2011.

In November 2013, she appeared Off-Broadway at the Minetta Lane Theatre in Standing on Ceremony: The Gay Marriage Plays. In January and February 2012, she starred in a limited run of Boeing-Boeing at the Paper Mill Playhouse in Millburn, New Jersey.

Leavel was cast as Bea in the musical Something Rotten! and began the workshop/reading for it, held in 2014. 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.”

In 2014, Leavel starred in the world premiere of the musical Dog and Pony at the Old Globe Theatre, San Diego.

She starred in the musical The Prom which opened on Broadway in November 2018. She was nominated for the 2019 Tony Award for Best Performance by an Actress in a Leading Role in a Musical.