agreeable person
嬖 centers on a person who is favored or agreeable, often with a nuance of being a favorite or beloved companion.
嬖 combines 辟 (likely a phonetic component) with 女 (woman), suggesting a woman who is favored or a favorite. The exact historical development is uncertain.
A woman (女) under a sheltering top (辟) is someone kept close and cherished: an agreeable favorite.
For ヘイ, imagine a favorite person named Hayley, shortened to 'Hey' (ヘイ), always greeted warmly: Hey -> ヘイ.