The abuse heightened Rihanna's celebrity and made her a household name. It was the hottest topic of that year before Michael Jackson died. I still remember Oprah talking to the camera and telling her, "He will hit you again!"

I don't think she's ever gotten as much press as she did that year.
She also was met with the best album reviews of her career while Chris was met with the lowest (he received a lot of 0-star reviews). 8 years later, Rated R is still her highest rated album on Metacritic.
I don't think there were immediate commercial results or anything tangible to prove the abuse was a benefit to her career. But in the overall picture of her as an artist, it added a compelling component to her story that helped transition her from an it-girl to an artist with depth and a story.
So, did it "help" her career? IDK. But it pushed her forward in the right direction and prevented a likely GGGB 2.0.