Based on how the characters of Dev and Sona were built in S1 and S2. Shall we make a wild guess on how things go against Sanjana in Ishwari mansion and how it all ends in a happy way....
My imagination......
Dev has actually told Sona what had happened between him and the psycho Sanjana that night but is only acting before lame Sanjana....
Sona is actually talking to Dev only when she went to check in Sanjana's friend house and also when she spoke about why this lady came from Kolkatta and all...
Last but not least our detective Dev intentionally told Sanjana that before Diwali celebrations itself he wants to get the culprit out and he is the one who actually involved media.....
That's how actually our S1 and S2 Dev and Sona should behave.....what do you think? Any guesses about how the story should end as per the standards it had before....