I think the police intervention was necessary...although the track could have been made a little more exciting. 😆
For one...the family had to be shown to have exhausted all means possible to save Devi from the hell she's going to face in the Rajavat house.
Second, I think it was necessary to bring Urmi's true intentions out in front of the family. She's going to have a lot of explaining to do as to what possessed her to take Devi's place.
Third, Kesar got a glimpse of the bride but remained silent. From this we know Devi has a sympathizer in Kesar. However, if Adhiraj or his mom picked up on this then she's going to be in even more trouble than she ordinarily is. So basically, Devi will have to stand up for her rights as well as for her own.