Daya, your topic reminds me of the movie Pataakha!
Spoiler Alert: Not sure if you have seen it, but the movie is about two sisters who could not see eye to eye and fought about almost every single thing. They elope with two seemingly very different guys only to end up in the same house as they turn out to be brothers and then when they decide to live separately to maintain peace, the sisters go through life altering changes because they could no longer fight with each other😆
The sisters there were generally similar and they had the same kind of issues with each other, so there was still a possibility of a middle ground. Someone could show them a mirror and there was a chance they would understand...
In our show however, the sisters are generally good people, love their families and want to keep them happy, but that's about as much similarity as you can find between them. Otherwise they are fundamentally just very different in their style, thinking, nature, approach to each other (let me help you even when you don't ask me v/s all my problems exist because of you), problem handling (this is wrong, let me tackle it head-on v/s it doesn't matter since family is happy unless the problem is you), their acceptance of each other (can I be accepted as family v/s wish you were/are not part of my life/family), extent of issue with the other (I will leave you alone if you leave me alone v/s I can't leave you alone as long as you are in my life), their basic idea of little joys in life...
I feel that they are just too different, especially when it comes to each other, to come to any middle ground at present. Distance would surely help, but won't completely eliminate the bitterness.
Abir might be able to help, but he will be torn between the sisters and is likely to lose his objectivity at some point or may stop if it ends up hurting Mishti and damaging his marriage in the process.
Parul is at the best vantage point to understand the issues between the sisters. She has kind of faced and been through somewhat similar issues with Benba as her pseudo-sister and learnt to make it work. And she also posses the wisdom that is required to convey her ideas without hurting the other person.
But overall, I feel it might take a life altering event for one, for the other to realize and change her viewpoint... till then, family can try to mend the relationship but it won't go far!