Purvi has a strong feeling that her mother is not getting her due, with no respect from her other daughters, and an impending divorce from her husband, somebody whom she loves dearly. So when the chance comes to demonstrate her love for her mother, when Ovi comes to her with a message that she will accept Archana as her mother if Purvi can get Arjun to marry Ovi, Purvi makes up her mind that this is what she will do.
So, she meets up with Arjun just on the eve of the marriage, hits him with the blow that she wants him to marry Ovi, something that he had already left behind, and be happy. Arjun is totally blown with this, but under blackmail from Purvi, finally agrees and does the marriage.
Even everybody in various sets of families are shocked, with Savita probably being the only happy one. Arjun told Ovi that this will not be a happy relationship; and even her family members know that Arjun had made his feelings towards Ovi clear in the past.