What was the need....

What was the need for Mohini to hatch such a plan as to have a Devyani wear the same bridal attire as Paro and to make sure Dilsher saw her in the bridal suit but not her face if no one was supposed to be there to witness it? Why would she want to make sure that Dilsher saw her if he was supposed to die in the fire? How the heck would he have been able to point the finger at Paro if he were dead????
If no one else was there to witness this and Mohini just wanted to point the finger at Paro saying she left the house last then what was the point in having Devyani dress up?

Is this just for us as viewers so the CV's can create this misunderstanding? Or do you think this was Mohini's way of having a backup plan for the plan she was was so positve was going to succeed...

P.S. Please ignore if this has already been mentioned, I looked at a few pages worth but didn't see anything at a glance...

For back up plan , what else