Because I think the big twist in the story is that Devika is only trying to protect Gauri from Mahen. Devika loves Gauri, because she regrets not being with her daughter before she died. I think Devika sees her daughter's spirit in Gauri.
Shiv is also not aware of this plan, but I think when he finds out the truth about his father. Shiv might side again with Devika to separate from Gauri but this time it might be for Gauri's own good. Because Shiv will love Gauri, and he wouldn't want her to be used by his father as an pawn just to get a land.
Then Devika during their separation might actually realize Shiv's real feelings. Shiv is hurting trying to break away from Gauri, she will see Gauri also loves Shiv and who knows this time she tries to protect Gauri's marraige and at the same time stop Mahen from acquiring that land. Devika will ask Shiv to fight his father if you really love Gauri. Alok might also find out the real truth of shashank disappearing, Devika and Alok apologize to one another for mistakes made in the past.
Then the real fight begins. Mahen the evil versus all the good guys. And in all this turmoil will be story of Gauri and Shiv's relationship.