Licking her wounds after husband Ashton Kutcher's September affair with 22-year-old Sara Leal, the actress, 48, "looked skinny but happy" at the intimate event, holding a hand-crafted Lanvin doll in her lap. (Each fashion show goer was given a doll, made by African women with HIV .)
The Margin Call actress was "very chatty" with fellow celebs at the party, adds the witness. "Demi came across the tiny runway to kiss and say hi to Katie Holmes," the observer says of Holmes, 32. Later in the evening, Zoe Saldana made a similar trip across the runway to kiss and greet Moore, who also laughed and chatted with Lanvin's designer, Alber Elbaz, throughout the night.
"The whole vibe was super friendly and relaxed," adds the witness. Moore's look for the evening included "nerdy glasses -- but [she] looked amazing. She stayed for the whole dinner."
Also at the bash: New moms Jessica Alba, Rachel Zoe and Kate Hudson with fiance Matt Bellamy, all of whom sat together. Hudson, 32, apologized for running late -- "she said she was breastfeeding," the source explains. (Hudson and Muse rocker Bellamy welcomed son Bingham in July.)