I agree with stummergirl's assessment of the "myth."
Streisand was in no position to throw her weight around on her very first film. They almost didn't cast her in it because she wasn't a "bankable" movie star. They wanted Doris Day for the part (no, I'm not joking).
So the studio was finally talked into green-lighting Streisand to reprise her stage role. She had zero clout as a film actress on this movie. She had a reputation as a singing star, a Broadway star, and a TV star ... but not a film star.
Her director was the legendary William Wyler, and she also says that the myths about her directing herself are untrue. She learned a lot while making the movie, and Wyler (and also Robert Wise) had a reputation of letting actors "do their thing" in front of the camera. They rarely made creative suggestions to the actors. When something wasn't working, they said, "Do it again." They didn't micro-manage the cast.
I'm sure it was Wyler (and perhaps the studio) who saw a rough cut of the (hugely bloated) film, and started cutting away at anything that wasn't essential. Both Wyler and Wise really "directed" their movies in post-production, working closely with their editors.
What was clear to all involved with "Funny Girl" was that Streisand was giving an electrifying screen performance. So her scenes were "essential," and everything else got trimmed or cut entirely.
She, however, had no say in that whatsoever.
"Jaws is the Citizen Kane of movies."
blocked: logan2, Diamonds3, Hamilton22