Since Ep1 I have been following closely all of Seo Ji Min's high school friend Choi Ro Sa shenanigans. Below is some of the things she been doing between ep1 -6. 

1.She appeared at the same bus stop with Seo Ji Min's boyfriend Park Ha Neuland ask him to share a taxi,
2.She is in the same photography class with Seo Ji Min and Park Ha Neuland but pretended she did not know she was in that class when they met outside like it was a coincidence....Not!
3. She sat right next to Park Ha Neuland at the drink up party and followed him outside
and got their photo taken to start a gossip.
4. She changed her classes to all of Park Ha Neuland's classes to get closer to him.
5. Choi Ro Sa dumped Seo Ji Min's cheer leader uniform in the trash but went to tell Seo Ji Min's boyfriend everything and it was meant to be a secret but she is the culprit, very jealous and want everything she has.
6. She took his photo at the photography class and she is not his girlfriend.
7. She bought the cake for Park Ha Neuland's Mom anniversary and his mom thought she was his girlfriend.
8. She is very jealous of Choi Ro Sa from high school and want to get with her boyfriend.
9. She saved the picture from the haunted room lol.
10. Seo Ji Min added Choi Ro Sa on the Movie plan and she is watching everything her boyfriend watches.
11. She got them couple's key ring, she has the same color (blue) key ring as her friend's boyfriend and gave the pink key ring to Seo Ji Min. Anyone notice anyone else doing so much?                12. Ro Sa called sick and got Ha Neuland to bring her study book to her house but it was a set up to have him there.