Who knows, but it could be Young-lan because she's pushing so hard for Jee-hae to be success. This will create a lot of controversy and a lot of $$$ for the video and film she plans to be involved with. Poor Jee-hae will be encouraged to perform, even as the dirt on her piles up, just to bring in more publicity. Maybe Young-lan is hoping that Jee-hae will become even more popular because people will feel sorry for her.
It seems that Jee-hae and Jae-min are a very naive young couple taken advantage of. Young-lan is very clever and cold, so she doesn't care who gets hurt.
younglan could be the obvious person since she does know everything that went on with jae-hae but with shows like these its usually the person everyone least expect. like DD or the guy that drives esm around.
i actually thought it was hilarious when jae-min's mom said that only family knew about the real story about jee-min. when she said that i was completely rolling my eyes cuz gossip on that show spreads like a wildfire. and also, the nosy coworkers from jihae's mother's office knows.... pretty hard to keep a secret on this show...