06/11/2012 at 02:00 PM EDT
Nicole "Snooki" Polizzi headed back to the beach to begin filming the next season of MTV's Jersey Shore
, and true to tradition, she hit club Karma on Saturday night – for the cameras.
But the engaged
reality star, who is pregnant with a baby boy
due in September, hardly seemed like the hard-partying girl viewers have come to know.
"She was sitting the whole time. It was very subdued of her," says a source, who adds that Polizzi, 24, did not appear to be drinking alcohol.
Also at the club were Snooki's costars, Pauly D, Mike "The Situation" Sorrentino, JWOWW and Ronnie.
As for the pint-sized mom-to-be, Snooki "looked nice in a little leopard print top and a leopard print purse," the source says. "It was probably the best I've seen her look."
A separate source close to Polizzi, whose spinoff, Snooki & JWOWW
premieres next week, isn't surprised by her low-key behavior.
"She is taking the pregnancy super seriously," says the source, adding that Polizzi has not been living in the same house as her rowdy castmates. "The health of the baby and her health come first."