Had a ‘big sis’ friend tell my naive and timid ass that saying a couple decades ago. Got reminded of it (not like that) today and had a chuckle.
For context, if a woman is wearing matching bra and panties it’s likely she knew you’d be seeing them later that night.
So, I’m curious, you think it’s true? Any other thoughts?


This makes sense in your context, but I am assuming that the context OP is discussing is the woman is going on a date that she knows will at least end up in her getting undressed enough that the other person will see her underwear.
Sure, but that’s still not necessarily sex?
One can also wear fun undergarments to a date and then decide not to undress or have sex - usually I think of it as “in case something happens” rather than expecting it from the outset. If nobody sees it, it’s not a disappointment, it’s just fun regardless.