Heigl, 36, portrays the title character, who shocks her traditional family by coming out as gay and announcing her engagement to her "roommate" Kitty (Alexis Bledel). The preview sees the couple plan their wedding as Jenny's family comes to terms with her revelation.
Beaches and White Oleander screenwriter Mary Agnes Donoghue directed the film and co-produced with Gail Levin and Michelle Manning. The movie opens in theaters July 31, and co-stars Tom Wilkinson and Linda Emond as Jenny's parents.
Heig is best known for portraying Izzie Stevens on the medical drama Grey's Anatomy, and went on to play Charleston "Charlie" Tucker on State of Affairs. Bledel starred as Rory Gilmore on Gilmore Girls and Lena Kaligaris in The Sisterhood of the Traveling Pants movies.