rihanna working with cops

R&B princess Rihanna is cooperating with Los Angeles cops, who have charged her boyfriend, singer Chris Brown, with smacking her around during a raucous argument early Sunday, according to reports.

The sultry songbird's injuries are "horrific," according to TMZ.com, which cited police sources.

Friends of the young star vowed to stand behind her. "Everybody's sick about it," said an industry insider who knows the duo. "She's so beautiful and nice. ... How do you hit her?"

Rihanna is providing "ongoing" cooperation with detectives, who are building a domestic violence case against Brown, a police source told the Los Angeles Times.

A key to the case could be a witness in Los Angeles' affluent Hancock Park neighborhood who called 911.

Brown, 19, and Rihanna, 20, started fighting inside his car, got out and continued arguing on a block of million-dollar homes.

"The screaming woke up my neighbors, but I slept through it," said Leslie Erika Klein, 62, who lives on the block. "My son saw them tow away the silver Lamborghini."

"I hope she's okay," Klein added. "It's a shame."

Authorities will decide whether to prosecute Brown, who had his first hit at age 16 and has spoken about his stepfather's history of domestic violence.

Brown was charged with felony domestic assault.

Police said Rihanna suffered bruises, while hospital sources said the "Umbrella" singer was treated for minor injuries.

Brown and Rihanna both abruptly canceled scheduled performances at the Grammys hours later.

"Rihanna is well," said a publicist for the Barbados-born singer. "Thank you for your concern and support."

Brown's image has already taken a hit - Wrigley Gum suspended an ad campaign he stars in until the case is resolved. On the surface, the dreamy couple looked happy when they appeared together at music mogul Clive Davis' pre-Grammys bash Saturday night.

"They looked lovey-dovey, laughing and hugging, whispering in each other's ears," a pal said.

But eagle-eyed observers noticed something wasn't right as Brown carefully watched Rihanna dancing with other guys. "Both of them are young and prone to jealousy," the pal said.

Good girl. Stay strong and don't go back to that assmunch.