Chris Brown and Rihanna at the Grammys
04/09/2013 at 11:00 AM EDT
once again dealing with a broken heart?
The subject certainly seemed to be on her mind Monday at a Staples Center concert in Los Angeles, as rumors of trouble with boyfriend Chris Brown
have begun to circulate.
"How many of you are in love? How many of you hate love? How many of you don't f––ing understand it? I'm in that group," Rihanna said on stage, before singing "What Now," from her most recent album.
The lyrics to that song begin: "I've been ignoring this big lump in my throat/I shouldn't be crying, tears were for the weaker days/I'm stronger, now what, so I say/But something's missing."
As she was soul-searching, Brown was never far away – literally.
A source tells PEOPLE the singer quietly entered the arena and watched Rihanna's performance from close to the stage.
Rihanna, meanwhile, was all smiles during the show, according to concertgoers, even encouraging the crowd to get a little rowdy.
"Los Angeles, what the f––k?," she said at one point. "I live here now, so I know y'all can get ratchet."
Rihanna and Brown, 23, recently reunited, despite the 2009 incident that sent Brown to jail. Rihanna recently spoke of her happiness at having a fresh start
Reporting by RAHA LEWIS, DAHVI SHIRA and JESSICA HERNDON