Rihanna And Amber Rose Have A Besties Pose-Off! (PHOTO)

Rihanna poses with Amber Rose backstage.

Rihanna and Amber Rose have a backstage pose-off! 

We're not even sure where to begin with this photo of Rihanna and new mama Amber Rose having a full-blown POSE-OFF backstage at Rihanna's "Diamonds World Tour" stopover in L.A. First, it's like, how is Ri's waist that tiny? We thought the 17-inch "Scarlett O'Hara waist" was just a myth from "Gone With The Wind," but apparently it lives! Second, how is Amber Rose a mom? Because aren't moms supposed to wear "mom jeans" with orthopedic shoes? Yep, just a few months after giving birth to baby Sebastian, Amber looks post-juice cleanse sexy, leading us to believe that she's one of those supermoms who gets zero hours of sleep and still shows up to party backstage at her famous friend's concert.

And Ri knows her pal Amber looks damn good too, writing, "Bad galz do it well! Miss @muvarosebud came thru and shut down backstage in this sick polka dot moment!!!" Yo, we fully agree! And if we may say so ourselves, Rihanna's been on QUITE the Instagram tear lately, documenting her "Pajamas On A Plane" moment as well as that one time she channeled Audrey Hepburn. Add that to her pose-off with Amber, and Rihanna's, like, the most active celeb on Instagram EVER. Now, on to more pressing business: WHO WON THE POSE-OFF? We kinda gotta go with Amber, only because of the whole "I just popped a live human out of my womb" thing.

Photo credit: @badgalriri