This is the 6751st most frequent Japanese word.
ヒロイン
"ヒロイン" means "heroine," referring to the female protagonist or main female character in a story.
In this sentence, "ヒロイン" refers to the main female character of the movie, which is the typical usage of the word as someone who is central to the story.
映画のヒロインは彼女です。
The heroine of the movie is her.
Here, "ヒロイン" is used metaphorically to signify someone admired and idealized by the subject.
彼女は彼にとってのヒロインだ。
She is the heroine for him.
In this case, "ヒロイン" indicates a specific female character from literature admired by the speaker.