I never knew 'helping' was interfering. :\
Yeah Naina and Karan agreed to the marriage because of the love they have for their elder siblings- Meghnal.
So out of love for their younger siblings, Kunal and Meghna will help and support Naina and Karan.
It's not only Nainas efforts that will get Karan better, yes she's made such a great impact on his life. He smiles more and is able to do things he couldn't before. To feel like he has fully recovered he'll need his whole family.
Meghnas anger always has a reason behind it, she's hurt and angered when , I've mentioned previously, 3 of the most important people in her life are hurt or in trouble or questioned; Sharda, Naina and Kunal.
Meghna doesn't know how Naina feels or that Nainas alright with it because Naina didn't share it with her. I don't know why Naina wanted to hide it away from Meghna because finding something out from someone else and not your own sister isn't the nicest feeling. Yes, Naina will try to explain to Meghna, Meghna won't listen because she feels betrayed and so there will be a small problem
My final point and opinion is that Meghna and Kunal along with the rest of he family can help Karan recover.
:)