For the sake of this post, please assume that Baba is not Nidhi's Nana. Actually, it does not really matter since they don't really have a grandfather-granddaughter relationship. He appears to view her as a daughter-in-law and she sees him as a father-in-law.
Now assume that Rohan walks back into Nidhi's life under such pitiable circumstances that Nidhi is forced to give him asylum. His dependence on her is so complete that she has to spend practically every waking moment with him and attend to all his needs. Baba sees the situation as a direct threat to his son's marriage and happiness. He requests Nidhi to maintain her distance from Rohan and offers to care for Rohan himself. Nidhi, who actually owes Rohan even when it comes to her relationship with Ashu, puts her foot down and says that Rohan needs her and she cannot abandon him. She more or less asks Baba to take a hike if the situation does not appeal to him. What should/would Ashu do under the circumstances?