IMO her insecurities have been intact, but the reasons have changed.
Earlier she was living strictly by the deal marriage. She doubted Virat’s past and their actions (their conversation in the balcony on Sairat 1st day in CN) and mostly Pakhi’s attitude towards her. This had strengthened belief that this marriage had no future. There was a night scene where Sai had fever and she was refusing to eat food or have medicine because of the morning incident. She told Virat, that she does not understand him. He scolds her sometimes and sometimes goes against his family including Pakhi to support her. He had told her that he supports what he feels is right. That has stayed with her. And then at all the occasions where Sai has confronted Virat on his friendship with Pakhi, he has never given her a clearly denied or given any clarification.
In the present scenario, the situation is fresh. Virat is guilty and she knows it. And she can rightly doubt his over sweetness due to that. But also, this had an emotionally difficult situation for both which had brought out their care for each other and love incase of Sai(unknown to her and Virat). They are just enjoying the attention they are showing on each other currently. And since Sai has decided to leave CN, her future off her relationship has been consciously pushed at the back of her mind