From reading the spoiler about Roshni proposing to Sid I have this huge feeling it will happen after she finds out the truth. She might realize that he had made the biggest sacrifice and that too for her mom. She was shown to be in a huge shock and saw Sid there. She had tears in her eyes. She was now in the know that Sid must have not wanted to divorce her but was put in the position to or else her mom would have been in trouble financially. I feel she will also realize now that she knows that Sid had told her how much he loves her, she might understand that he does not care about the commitment, so she might as well tell him her feelings. Also, Sid might feel that Roshni is angry at him for keeping all this from her, so he might try to explain to her. She might not respond quickly to him, but through the song she might tell him that she loves him, will always be by his side forever and that she forgives him. I feel with her knowing the truth and then singing to him will show others that there is nothing that can keep them apart and also reassure Sid that Roshni is just as much there for him as he is for her.
This is just a prediction, but I do really hope she sings to him after finding out the truth from Simran. I do not want it happen after the song sequence...
What are your opinions and predictions??