Kyle Richards is hitting back after Garcelle Beauvais questioned her sexuality on camera ... blasting her "Real Housewives of Beverly Hills" costar for acting like an "ass****."

The longtime Bravo personality issued a biting response to Garcelle seemingly encouraging her to come out as a "lesbian" during Tuesday's episode ... and accused her castmate of trying to get a reaction out of her on the 'RHOBH After Show.'

While Kyle noted she was unbothered by the line of questioning -- since rumors about her sexuality have been ongoing amid her friendship with singer Morgan Wade and her separation from husband Mauricio Umansky -- she admitted to being confused by Garcelle's motive.

She added ... "What was really going through my head was, 'You're being an ass**** right now and don't try to act like oopsie-daisies. You know exactly what you're doing.'"

Garcelle has an entirely different takeaway from her conversation with Kyle, though ... she explained on the after-show that she felt she was just encouraging KR to live her truth -- whether it involves a lesbian lover or not.

She noted ... "I'm not trying to call her out. Own it. Be authentic. 'Cause, I feel like Kyle cares a lot about what people think and how this is gonna look."