Jackson Lee/Splash News Online
After the opening night of previews of Dead Accounts
, Katie Holmes
hosted a small party at The Lambs Club in New York on Monday.
"Katie came into the party wearing sunglasses," an onlooker tells PEOPLE. "She stayed for about 45 minutes and put the sunglasses back on when she was leaving."
Dressed in "a beautiful flowy black pantsuit and white shirt," Holmes mingled with her guests as they enjoyed Hemingway daiquiris, shrimp tartines and tuna tartare.
Although she made a brief appearance, while in attendance, Holmes – who made her Broadway debut in 2008 in a revival of Arthur Miller's All My Sons
– was in "good spirits" and spent a lot of time with costar Judy Greer
, the source adds.
, written by Theresa Rebeck and also starring Jayne Houdyshell and two-time Tony Award winner Norbert Leo Butz, officially opens Nov. 29.
– Suzanne Zuckerman