Till now neither sai nor pulkit mentioned about harini. I don't think CVS forgot harini during the scene. Since kaku asked pakhi to stop marriage they need something. virat already know the lady with pulkit is his sister, so harini can cause misunderstanding. May be sai and pulkit kept harini ad surprise and when pakaku tell others about her they won't believe them and may misunderstand sai too which can lead to separation. Later either by DNA test or from school records virat will come to know the truth and realize mistake.