Last night a bra-less Rihanna and a girlfriend went to Las Palmas in Hollywood, and the R&B superstar was NOT in the mood to have her photo taken. Maybe she was feeling a little stressed over work and the drama with her on-again/off-again beau, Chris Brown? That's our best guess...

After spending the day at the studio doing voiceovers for the upcoming animated flick Happy Smekday, RiRi tweeted, "Had a blast today! So weird recording for animation, but I get to keep my accent! AND it's PG, which mom should be happy about! Brrrap!!" So what was next on her agenda? Party time! Rihanna wrote, "Mama gets to blackout TONIGHT!!!!"

Hope she had fun!