Corinne Olympios and Boyfriend Jordan Gielchinsky Do Lunch Amid 'BiP' Sex Scandal

Corinne Olympios and her BF are putting up a united front during her "Bachelor in Paradise" sex scandal with DeMario Jackson ... even if they're not talking about it.

Corinne grabbed some lunch Saturday in L.A. with Jordan Gielchinsky, carrying on like your average couple ... even though their situation is anything but. Both were mum on Corinne's next move.

We broke the story ... Jordan is standing by Corinne in the midst of the investigation over her sexual encounter with fellow "BiP" contestant DeMario -- despite agreeing she wouldn't hook up on the show. Corinne says she was out of it and it wasn't consensual.

Classic move by a good beau.