Malice (2015)

Ga-In's (Hong Soo-A) family went into financial difficulties when she was a college student. One day, she happens to meet Eun-Jung (Lim Seong-Eon). They went to the same high school. Unlike Ga-In, Eun-Jung seems to have everything including a happy marriage life and stable job. Ga-In feels jealous of Eun-Jung and soon she becomes obsessed that she is Eun-Jung.