WhizzerMarvin, the show is based on her book by the same name, so that might have what you're looking for, although I'm sure the show has marked differences.
At first I thought the people she interacted with were planted in the audience, but I honestly don't think they were. At the most, they were tapped on the shoulder before the show. The only thing that had me skeptical was how well the one guy that came onstage projected his voice. Either way, though, totally fun night.
2010
Feb. 28 - Looped, Feb. 28 - Next to Normal, March 4 - Hair, March 11 - A Little Night Music, March 24 - Time Stands Still, April 6 - La Cage Aux Folles, April 10 - Anyone Can Whistle (City Center), April 10 - Looped, May 9 - Enron, May 15 - A Little Night Music, May 15 - A Behanding In Spokane, May 30 - A Behanding In Spokane, May 30 - A Little Night Music, June 20 - A Little Night Music, June 23 - Red, June 23 - Sondheim on Sondheim, July 13 - A Little Night Music, July 18 - The Grand Manner (Lincoln Center)