She does know from experience. He trained her in the Red Room. He doesn't remember her, and we've seen no evidence in the MCU that she remembers him from the Red Room, but these two DO know each other.
Steve and Sam learn a bit of Russian to get what the Russian ex assasins are up to until Bucky and Natasha figure it out and continue doing the same thing but this time in German
and ... "Tony Maybe?" a Psychoanalysis by Bruce Banners "Fuck You Tony" a Memoir by Clint Barton and Natasha Romanoff "Tony Stark: a Generation of Motherfcking Recklessness" a Historicist criticism by Nick Fury "Die Tony Die" a Postcolonial Fiction by Wanda Maximoff "Stark's missile: seen that coming?" a sensationalist novel by Pietro Maximoff