I like this new character; she adds a lighter atmosphere to the drama. I think the story is trying to paint Hwayeon and Jisoo as being exes, but they obscured the person's face on pg. 13-14. If that was Jisoo, why hide her face? Was that even Jisoo?
From Jisoo's dialogue (honestly, it's a little oddly phrased for me, but I'm reading this chapter and writing this comment on 4 hours of sleep), it seems like Hwayeon has a history of breaking people up or at least meddling with their love lives. Did Hwayeon get in the way of Jisoo and a former girlfriend? Or, if we're going by the bitter exes route, maybe she cheated on Jisoo? If so, I wonder if that's why Jisoo is pursuing MC. She knows that Hwayeon likes her, so she's going to take MC away.
Regardless, I like the direction that this story is going, and I'm glad to finally see things picking up.