i think there was always a duality in ridhima's character to begin with..which striked me as funny.
i mean she was all sporty on the basketball court from day 1..wanting to bring armaan's ego back to the ground..but then when she used to take the BS anjali used to give her (just as an ex), it showed a different side to her, an obedient bholi bhali side.
and i think the reason she was giving armaan trouble was b/c she considered him unable to commit to one girl (which i totally disagree with and think he's proved himself quite a few times). nevertheless, i really hope she sees that finally this time!