“He writes (and oomis1105 repeats it): ‘yichud is prohibited [with an unmarried woman] and has the severity of yihud d’oraisa ,due to her being a nidah.”
I never said that. That was Geshmakenstein’s quote, not mine. All I did was ask for the makor where it states that a kallah is erva to her chosson, and therefore should not be complimented by him or vice versa. I wanted to know the exact source for that. I made absolutely no comments about yichud d’Oraisa or otherwise.