Translation

女性の相談相手 / 信頼できる女性の友人 / 腹心

Meaning

A confidante is a woman you trust with private thoughts, secrets, or worries. The word is less common than friend and can sound literary or careful. The learner trap is confusing confidante with confident, which means sure of yourself.

Examples

• 彼女は母を一番信頼できる相談相手だと思っていました。
  She considered her mother her closest confidante.
• 女王は長年の女性腹心に秘密を打ち明けました。
  The queen shared the secret with her longtime confidante.