But don't stay out too late, Nic - baby Harlow probably misses you back at home!

Joel Madden's babymama was spotted in an Escalade with a friend last night, parked outside a pal's house in West Hollywood. The two chatted for a bit with the interior lights on...

Be good, Nicole! After this week's alleged "catfight" in Vegas, let's hope the reality star isn't slipping back into old habits!