anniebella:
https://mydramalist.com/character/kang-eun-ji
The actress wasn't in Happiness. (She has Naver and Namuwiki profile - without Happiness mentioned as one of her dramas.) It was an other actress with the same name (without Naver and Namuwiki profile) who played the character and she doesn't have a mydramalist profile page.
What episode did the character Kang Eun Ji appear in?
The source, whether accurate or not, got the info from the Hancinema page for the actress: Kim Ju-yeon (김주연) @ HanCinema or their drama cast page: Happiness - Drama - Cast (Korean Drama, 2021, 해피니스) @ HanCinema
I don't remember the character Kang Eun Ji, but it's easy enough to tell which is which since one of the Kim Joo Yeons is 29 and the other 48. The 48 y/o has no credits since 1997, though, on Hancinema... and it isn't likely the [disqualified bc of a scandal] 2007 Miss Korea turned YouTube fitness influencer either. :)
Naver and Namuwiki are NOT complete authoritative profiles... they're both missing her smaller roles, so it's quite possible that since she does guest/bit parts (she's primarily a musical actress), she could easily have been a Zombie etc in Happiness and be missed. In general, we're required to attach a screenshot of the character Kang Eun Ji IN the show to properly disprove Hancinema's citation... that's what they've asked me to do when making such edits as removing/changing cast, at least.