Terms to know/ Clarification

Hwasa and Wheein have been friends for years. They became friends after realizing they had the same dream, suddenly Hwasa gives up on the dream. Wheein follows her footsteps. A series of events lead to Wheein's selective memory loss. She says those memories are her happiness and vaguely remembers them when she's dreaming... What are these memories? and will she ever get them back?