confidante

詳細解釋：

con.fi.dante

n.（名詞）
A woman to whom secrets or private matters are disclosed.
紅粉知己：一個可以對其傾吐秘密或私事的女友
A woman character in a drama or fiction, such as a trusted friend or servant, who serves as a device for revealing the inner thoughts or intentions of a main character.
戲劇或小說中的一個女角色，如作為主角的密友或僕人，來揭露主角的內心思想和意圖

來源：
French confidente [feminine of] confident [confidant] * see confidant
法文 confidente [] confident的陰性詞 [密友] *參見 confidant