As they expose more & more of Kalpana, she has a rather unique appeal.
Since Appu is too shy and refuses to befriend anyone, it's up to Kalpana to make her, or Malloy's attempts to romance her will fail. Now, the reason she wants to encourage this is so that Appu accidentally kills Malloy and Kalpana has her revenge on the Mittals. But since she's the one enabling Malarajita to come together, that's the only reason to root for her in the show.
However, although Kalpana is encouraging the closeness b/w Malarajita, I do believe that she has a limit. Since her objective is to kill Malloy, she can't be okay w/ Appu herself falling for him and marrying him. She'd like her to kill him b4 that happens. She wants to destroy Malloy but not her daughter, but that can't happen if her daughter marries Malloy, or she will risk being widowed.
I think Dida can sabotage Kalpana's plan by encouraging Appu to marry Malloy in Kalpana's absence, so that Kalpana's plan to kill him is forced to be revised. Unless Kalpana turns out wanting to make Appu a widow as well.