At first, I thought Sujata was not interested in getting married. Then we began seeing her silently liking Raghav, and thanks to Raj... she finally admitted her feelings. And today when her sisters were cheering for her when they realized there was a rishta for her, Sujata was overjoyed and shy... like a typical girl who's happy to get married to a guy whom she likes. Which means she's not against getting married. After seeing her parent's reactions, its clear they're the ones against it... and Sujata doesn't know why they are against it.
So now the question arises... why would they not want her to get married, esp when the rishta came right to their door, and it was all pucca and all? But they seemed adamant in not letting her get married. This is what I think could be the raaz the parents are keeping from everyone.
When the kids were little, maybe the parents got Sujata married (like a child marriage). But Sujata may have been too young to remember it now, and her parents too haven't told her. Maybe they didn't tell her, because the guy whom she got married to grew up and changed his mind and possibly fell in love with someone else. His parents may be trying to change his mind and have asked Kulraj n Kohli to wait till they can convince him to accept Sujata as his bride. So since she's married, obv they can't get her married to someone else; that would be clearly illegal.
This is what I think, wud love to hear ur views as well. :]