My theory regarding Avni is this.
1. I think she and Ahir formed a plan to target the Ranes. Cause Ahir was disowned, so whatever money was left went to Kaka, Swara and Malhar. And since Kaka had no children, money would Malhar and since Malhar had nor children, money would come to Avni and her child. That much is clear. It seems that she truly liked Ahir only. But Ahir didn't care about her, he just wanted money and badla. So I don't think he told her that he kidnapped Moksh.
2. The day Ahir died, I'm feel like Avni went there to help Ahir but she accidently ended up killing him. Like she was trying to move the beams that fell on him, but it ended up killing him instead and she also miscarried. So she used the opportunity to gain sympathy and get married to Malhar.
3. Since she couldn't get married to Malhar and Moksh was found, and KalMa were gonna become a happy family, I think she killed Malhar. Cause if Moksh is there and KalMa have more children, chances of her getting anything is low. I believe based on her reaction in the precap that she killed Malhar and trapped Anu.
I feel like there must be someone else helping her out. Cause there is no way she's doing all of this without anyone's help.
that means now malhar must be knowing her true colors already and his death scene was indeed true but he survived and came back with the mission to catch her and the gang she has connections with and that might be the same gang that kidnapped moksh?