Well said initially no one were aware of who she's in fact they waited for her in the yard when she arrived with her husband and children no one was shocked either.
The part shown where Vedshree and Chaitali went searching for Mohana asking everyone on the road with her picture in hand if ever they have ever seen this girl in this city proved that they were stranger but suddenly they are sisters...
If Vedshree and Mohana were sisters then why Vedshree was searching for Mohana real identity why she was shocked on seeing her burnt house well Vedshree and Mohana being sisters were decided overnight...(Change in story)
Mohana is a witch she was the one who killed her husband then initially I think she would have tried to lure Shekhar nothing was shown...