Hach graduated from the University of Colorado at Boulder's School of Journalism, and later worked as a research assistant at The New York Times Denver bureau and as a magazine editor at Sports and Fitness Publishing.

A 1999 recipient of the Walt Disney Screenwriting Fellowship, Hach wrote the screenplay for the 2003 remake Freaky Friday with Leslie Dixon, and both were nominated for a Saturn Award for Best Screenplay for the film.

Hach wrote the libretto for the 2007 musical Legally Blonde, based on the Amanda Brown novel and the 2001 film of the same name, and was subsequently nominated for a Tony Award for Best Book of a Musical and a Drama Desk Award for Outstanding Musical. In 2008 Hach appeared on MTV's The Search for Elle Woods, a series created to find a replacement for the lead actress then appearing in the musical on Broadway.

Hach is the co-author (with Mary Rodgers) of Freaky Monday, a novel to be released by HarperCollins on May 5, 2009.

Hach married Jason Hearne on December 23, 2003, and the couple has a daughter, Harper, and a son, Drake.