The lead actress in this movie was really well cast.
The female lead in this movie was perfect for the role/part.
「役」は「role」「part」と言います。
「cast」は「役者を選ぶ」という意味です。「well cast」は「上手く役者を選んだ」という意味です。つまり、その役に合っているという意味ですね。
「役に合ってた」は直訳したら「she fit the role well」になりますが、あまりそういう英語は聞いた事ないです。
The actress who played the lead female fit the role really well.
The actress who played the main character fit the role really well.
■キーワード
actress = 女優
lead female = 主役の女優
main character = 主人公
fit the roll = 役に合う
①The actress who played the lead female fit the role really well.
→ 主役を演じた女優さんがすごく役に合ってた。
②The actress who played the main character fit the role really well.
→ 主人公を演じた女優さんがすごく役に合ってた。