Figured it out

Ok! Gaeul Jin was the main character in Gaeuls flower. She was the friend of the older college girl who dated hamins brother before he became unalived.

Soobin was originally part of the group who bullied G if I remember correctly. There was a girl in the group who liked Soobin, and whenever she was angry, she would take it out in G.

Soobin and G never dated, but they said they would if they met later in life.