I think Hyejinie spilt the beans when she said Hwa Night. You can see her "oh shoot" face, and tried to remedy it by continuing to act like she's parodying Byul on Moon Night and said stuff about Byul being busy even though she didn't need to. 👀🤣😌🥰
UPDATE: Byul used the cooker during camping, and called Hyejinie when she thought of her!! 🥰🥰 ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-JTEzDtUxoNQ.html
Moonbyul's name in Chinese characters is 文星, wen xing (Mandarin) or mansaeng (Cantonese). They learned it when they visited Hong Kong. Hwasa loves calling Byul that, it's her fav nickname for her.