Cara Delevingne Shnoystering Sienna Miller ... Which MIGHT Be Hot???

5/5/2014 5:45 PM PDT

Just when we thought Cara Delevingne had moved on from Michelle Rodriguez ... and picked up with Sienna Miller -- CD dropped a "SHONYSTER" bomb.

Yeah, the word was a mystery to us too ... but now that we've figured out it has nothing to do with oyster shucking, clam digging, or any kind of seafood ... we're kinda bummed.