The actress is Shamim Ara. She is now retired. In the early seventies she retired form acting and became a film producer and a director tll late 1990s.
The story of the film is that the boy in this film has amnesia nd has fogotten his past, the opart when he was in love with her, so she sings ths song. The meaning of the first few lines of the song is as below.
It's good that you have forgotten everything
My love was a big mistake anyway
My heart's garden was on fire, how could flowers bloom there
We were two branches of one river, how could we get unite?