Nicole Richie was in the audience at Britney Spears' concert last night at the Staples Center, and we have a feeling she was scoping out more of Brit's moves!

In a video posted by Nicole, Harlow and Sparrow's mom proved she's got rhythm ... especially when it involves a Britney Spears dance off. In addition to the video, Nicole Tweeted:

    "In honor of my queen, @BritneySpears - Can't wait to dance tonight!"


We'll admit, Ms. Richie's workout classes with celebrity trainer Tracy Anderson are paying off.

Wonder what Brit thinks of Nicole's "Slave 4 U" moves? See Nicole and her BFF Paris Hilton arriving at Ms. Spears' concert in the video below. During the show, Britney gave a lucky fan a lap dance. Check it out ... after the jump.