If you go back to the start of the show then the main culprit was the manager who used Sid's name to demolish Roshni's NGO. If the manager had not done that, then Roshni would not have hated Siddharth Khurana nor would have Sid had to lie. Roshni would have loved him regardless when she would have seen that being rich there are nice people. Simran would not have necessarily hated Roshni and so on. But at the same time it is a TV show and it would not have been fun to watch without the drama. LOL!!
Well, now she is seeing how great of person Sid and Raj are regardless of being rich more rich than DD.