If Shabnam finds out about Raghu being Sid within the three days, she is bound to attack again. I'm thinking she might try to harm Roshni again by keeping Sid tied up or something so he doesn't try to save Roshni. But I feel she might not kill her but injur her. As a lusty person she is her goal would be to make Roshni see her all over Sid against his own will. Making do things Shabnam's way or else Roshni dies. Roshni might be injured badly and Sid might be in a sticky place. But then DD of all people could come and save them by bringing the police.
It sounds odd and it might be painful to watch but on the plus side we would be getting a lot of emotional SidNi scenes which we know NiVi do wonderfully just as they do the romantic scenes...drama loved by TRP aunties...lol!!