I mentioned it in the Kalpana thread - that I don't think Kalpana will want or allow Appu to
marry. She wants to kill Malloy, so is using her daughter to get to that end, but if Appu
marries Malloy, that would mean she becoming a widow if that happens. So she's doing what she can to encourage friendship, and even a relationship, but not marriage. It would be interesting to see how she plans to prevent the latter, having encouraged the former.
I think Dadi might be the one encouraging Appu to marry to sabotage this plan. After all, as long as Appu is not married to him, their being together threatens no one but Malloy. But if they are married, Appu killing him would mean making herself a widow. I doubt that Kalpana wants Appu to be that.
She'd probably want Appu to drain all her poison on him, so that she can be normal again. Then she'd be free to raise Appu anyway Appu wants to be raised - be it locked in forever, or married off, or whatever