09/05/2012 at 06:00 AM EDT
Girls just wanna have fun!
stepped out on Saturday night to celebrate the launch of shower accessory Raindrops at Nine Zero One Salon in West Hollywood.
"She was just really happy to have a girls night out," an onlooker tells PEOPLE. "She walked in laughing and was joking around the whole time."
Staying close with her girlfriends the whole night, the new mom was upbeat, listening to a mix of '90s and current pop hits.
Also in attendance: Project X
's Alexis Knapp, Dallas
star Josh Henderson and singer Leona Lewis, who was spotted dancing to the older jams with her friends.
– Melody Chiu