She was seen comforting Brown at a pre-Grammys party just hours after he banged into a wall on Saturday.
"Rihanna is just relieved Chris is okay. She was like 'what the f**k' when she heard he lost control of the wheel. She blew his cell up and panicked even more when he didn't pick up," contactmusic.com quoted a source as saying.
"But then he called her back like 20 minutes later and told her he was 'all Gucci' and couldn't pick up because he was talking to the cops," added the source.
"After Rihanna talked to him, she took a deep breath and told him to 'be careful.' She asked if he needed anything, but he said 'he had everything under control'. That scared her though," said the source.
Brown, 23, has blamed paparazzi for causing him to lose control of his Porsche, but they deny the accusation.