Slipstream never really told to Starscream from what side of his personality he was created, saying simply "Don't Ask." But it's obvious that of all the clones, she's his affeminate side.

Derrick Wyatt (bless his soul) made a lot of references in Transformers Animated to past series, including the japanese ones, even adding characters originally created for the infamous Kiss Players.
He was obviously a fan and something tells me he knew of the international French dub of the animated movie from the 80's where they gave Starscream a female voice and pronouns.