Well that didn't last long!

Page Six reports that reality show winner Shayne Lamas and her Bachelor fiance Matt Grant have called off their engagement - because she cheated on him! Who's the, er, lucky new guy? Media mogul Justin Weneger, shown above with Shayne and Jeff Beacher at Ago in Vegas this weekend...

Reality TV shaynenewguy.jpg

...he was also at the Wasted Space opening at the Hard Rock, too.

And get this! An X17 source says Justin asked Shayne NOT to walk the red carpet with him at the event - damn, he already knows how to play the Hollywood game!