I think, I could be wrong, this is going exactly how I thought it was. Sunbae can tell they both are in love with each other and she thinks they're both idiots. Woo-Hui took her damn time but finally got to where she needed to be. Jiho is afraid, and maybe traumatized, with the idea of losing her friends and is also afraid that ultimately Woo-Hui is straight, even with the confession.
It seems like Sunbae is now permanently out of the picture (romantically anyway), so there's really nothing holding them back except their own fears. Or really, Jiho needs to be a little braver.
Also, I forgot this but the blonde drunk girl was also in chapter 48 where Woo-Hui basically told her, so she probably knows they hooked up. Her suggestion for them to kiss and make up is extra funny knowing that.