I also don't like the behavior of Yash's girls, but at the same time I can't blame them. When children are young, their behavior reflects on the way their parents brought them up, and without a proper upbringing children cannot be well-mannered. While Ansh did not have a father figure in his life, Aarti did a good job bringing him up. Plus, he grew up in a positive atmosphere with a doting mother and grandparents who loved him. On the other hand, Payal and Palak grew up with a father who is always lost in thoughts of his wife. While he does take care of them, it is sometimes mechanical and he has failed in teaching the kids basic manners. Not only Yash, but Yash's parents were probably not as affectionate or doting as Mr. Dubey and Shobha, and since the others in the family are always busy wit their own lives, Payal and Palak never really had anyone to teach them anything.
Also, they must be feeling insecure that Aarti might usurp their position in Yash's life. They were after all Yash's sole reason for living after Arpita died, and to suddenly have another woman enter their father's life cannot be easy for them. Plus, no one even prepared them for it like Aarti prepared Ansh.
The basic problem is that no one really talks in the Scindiya household...they all are lost in their own lives so Payal and Palak have only their father who thinks of them 24/7, but he only fulfills their materialistic needs and hasn't really attended to their moral upbringing. Hopefully, Aarti will be able to fix that soon.
