They definitely put her in too soon. The thing is, she was really great in the role (even though I thought they could have found a better look-a-like), and one of my favrite scenes is when she's in the backyard and snaps at little Liza...then runs over to apologize. So like other were saying, she was still married to Vincent Minnelli at that point, so it would be weird if they switched actresses while she was still with the first (well, technically 2nd) husband...though I don't recall if they mentioned her real first husband in the movie? Or her abortion?
"It's the little things; the details, that distinguish the Barbra Streisands from the Rosalyn Kinds."~Gilmore Girls~