You hit it on the nose. I remember there was a post comparing Angad to Arnav and how Sahiba was better than Khushi. I'm not even a big fan of IPKKND, but even I'll have acknowledge that they did this hiding truth better than TMD.
Arnav, for all his flaws, was a product of having seen his mother shoot himself right before his eyes, before being made homeless in a span of 24 hours. He was hard-nosed due to circumstances and detested Khushi for being completely opposite to him and having to repel the lust and attraction between both of them. He doesn't believe in goodness or purity or love because of his circumstances, believes in the power of money which he single-handedly earned, which does not excuse his behavior but at least makes him three-dimensional. Angad.....just dislikes Sahiba. That's his storyline with her.
Khushi, when she knows of Shyam's deceit, inspite of objections from her family, decides to tell Anjali the truth and only relents when she notices how disturbed the latter was about even her mangalsutra breaking. Her guilt about hiding the truth is evident throughout the show and most of all, she reaps her punishment for hiding it - a horrible marriage and a vengeful husband who doesn't believe her.
I don't even want Sahiba to not support her mother/sister because it wouldn't drive the story forward. But the least they can show is how the immorality of their actions is pricking her conscience. At least that would show us her goodness. Because no matter if it was the original, no matter how they twist it, she is cheating Angad and the Brars. Hard to feel sorry for justified karma heading her way.