What actress and singer who played a starring role in "Grease" was a special guest during the Mormon Tabernacle Choir's 2015 Christmas shows? 
Hallelujah! (Mormon Tabernacle Choir album): Hallelujah! Hallelujah! (Mormon Tabernacle Choir album):  was recorded during the Mormon Tabernacle Choir's 2015 Christmas shows in the LDS Conference Center, with special guests Broadway star Laura Osnes, actor Martin Jarvis, and guest soloists from the Metropolitan Opera (Erin Morley, Tamara Mumford, Ben Bliss, Tyler Simpson). Laura Osnes: Laura Ann Osnes (born November 19, 1985) is an American actress and singer known for her work on the Broadway stage. Laura Osnes:  She has played starring roles in "Grease" as Sandy, "South Pacific" as Nellie Forbush, "Anything Goes" as Hope Harcourt, and "Bonnie and Clyde" as Bonnie Parker, for which she received a Tony Award nomination for Best Actress in a Musical.
Laura Ann Osnes