I tried to track the history of the “translation is like a woman/mistress…” quote, but I haven’t been able to track it far in a brief search. It’s been attributed to “Russian proverb” and to an Indian filmmaker and writer. Using Google N-gram turns up many other metaphors for translation (Cervantes’ “a translation is like looking at the other side of a tapestry”, or “a translation is like looking through a piece of glass”, or many other sentiments), but doesn’t seem to have the one in the title of this thread. Even Wikiquote and Quote Detective seem to be silent.
I haven’t time to look into it now. But this silence doesn’t speak well for this being an old or possible even an authentic “Russian proverb”.