04/27/2012 at 05:55 AM EDT
Minka Kelly was feeling fishy on Wednesday night when she popped into Pearl Dive Oyster Palace for dinner with two friends in Washington, D.C.
Tipping back a dozen raw oysters, the actress gave her pals a hands-on demonstration of how to slurp down the delicacies, in between munching on blue crab cakes and Kentucky Derby pie.
"She [seemed] very happy," an onlooker tells PEOPLE. "[The group] was all laughing with each other. Minka was very sweet, at ease and casual. She [seemed] really fun."
Kelly was in such a good mood that when she was approached by a fan who was being deployed to Afghanistan the next day, she ended up paying for his meal.
– Helin Jung