"Girl shut tf up!"
That's how Skylar Diggins-Smith responded to some shade Jazmine Jones threw her way this week ... and, yeah, there's now some Grade A beef going down in the WNBA!!!
The epic clapback from the Phoenix Mercury star went down Monday afternoon ... after she saw an IG comment Jones had left on one of her highlight videos.
Bleacher Report had posted footage of Diggins-Smith destroying NY Liberty rookie DiDi Richards during their game Sunday .