Sahir mentions dhokha-fareb. It would mean that he was cheated by this woman.
Maybe he was forced into the marriage.
When he found out about the infidelity, he lost control and maybe beat her, due to which she has gone into a coma. KA unknowingly witnessed all this and used it as a blackmail point to Alvira.
Sahir has enough clout with the police to hush up the case (or maybe Alvira has done it that way). But Sahir feels guilty and has cared for his wife. KA doesn't want him to move on but Alvira wants to.
Maybe this is what Alvira meant "asp me mansoobe JAL rage gain"
And there is this legal tangle:maybe Saiyyara belonged to Zeenat. And was willed to Sahir due to their marriage. And this is captured in the legal document that Ansari brought that day. Maybe Zeenat's nikahnama?
I am scared to even contemplate Alvira's future course of action, now that Zeenat has come out of the Coma. How would she get Arzoo marry Sahir? Murder Zeenat?