Demi Moore walked the red carpet by herself at Monday's premiere of her dramatic thriller Margin Call at the Landmark Sunshine theater in downtown Manhattan.
In her first official event since Us Weekly broke news of husband Ashton Kutcher's one-night stand with 22-year-old Sara Leal on their sixth wedding anniversary, the 48-year old star put on a stoic smile in a printed red sheath dress that accentuated her increasingly slim physique. Also part of her ensemble: Her wedding ring from Kutcher, 33.
"Everyone was remarking how thin Demi was, more so than usual," an observer at the premiere tells Us. "She seemed in a decent mood though, even a little happy to be there."
After posing for pics on the carpet, Moore skipped press interviews and headed into the theater -- and enjoyed a round of applause and acknowledged the audience when director J.C. Chandor introduced her.
"She was having some issues with her dress," the observer adds of her tight outfit, noting Moore nearly tripped. "Then she headed out."
Moore bailed on the flick's afterparty held at the Top of the Standard Hotel, where costars Zachary Quinto, Stanley Tucci, Simon Baker and Penn Badgley (with new love Zoe Kravitz) celebrated their buzzed-about film.
Despite her cheerful mood, Moore's shrinking figure has her friends worried. "She's very upset, and hasn't been eating," says one source. Her husband's infidelity and the state of their marriage is "taking a toll," the source added.
Moore's husband Kutcher also made his first official post-scandal appearance over the weekend -- presenting solo at Bill Clinton's "Decade of Difference" concert/fundraiser in Hollywood.
Introducing a performance by Usher and chatting about his "DNA Foundation" co-founded with wife Moore, Kutcher appeared to be wearing his wedding ring as well.