The Yellow Robe (1967)

Cyril (Tony Ranasinghe) is dissatisfied with his introverted fiancée Sujatha (Punya Heendeniya). He starts a relationship with the outgoing Sarojini (Anula Karunatilleke) and gets her pregnant. Sujatha meanwhile is fascinated by a wandering Buddhist nun.
Due to the pregnancy, Cyril breaks off the engagement having no intention to marry Sarojini. Till the birth of the child he supports her and then leaves her for an older rich woman. Sarojini is distraught and contemplates suicide. Sujatha by this time is planning to become a nun.