When the going gets tough

Sam articulated the essence of Ishwari-Sona conversation beautifully. In a set of complex series of reactions this is the first and irreversible one. Sona was slowly chipping away at the wall, this was the blow which hit at the right spot and the whole wall came crumbling down. Like you say it is a very complex dynamics; having a grandchild was probably the only positive thing that Ishwari was expecting from Dev's marriage for all the reasons that you've mentioned. Her biggest fear with this marriage was that she will lose control over Dev and will lose everything that she has worked so hard for. When mami spoke to Ishwari about Sonakshi not wanting to have a baby immediately reinforced Ishwari's belief that Sona would always put her dreams above the wishes of the family i.e. Ishwari. For Ishwari, the news of the baby was as unexpected and she believes it is because Dev convinced Sona to reconsider their decision for HER. So when she acknowledged to Sona that her fears were baseless it is with this perceived knowledge that her control over Dev's life is absolute.

With the aftermath of Dev's illness she had conceded that stubbornness and insecurity is costing her children, maybe Dev's life and definitely Neha's marriage. That has awakened the protective mother in her which had been lulled in the wake of the position and wealth Dev has now acquired; so when Ayaan's truth was brought out she chose to act wisely. It was an eye opener for her that she is destroying the very thing she is trying to protect by letting her insecurities cloud her rational thinking. The insecurities have been acknowledged doesn't mean they are gone but the realization of the havoc created by her actions arising out of the insecurity will prevent her from acting on it when it rears its head again. The news of Sonakshi's pregnancy is letting her make these rational decisions and not because of it as perceived by Dev, Neha, mami and most of us viewers. This is what makes Dev's actions of hiding the news of this pregnancy totally stupid, unnecessary and the catalyst for the next reaction.

The "parallel reality" that Dev is chasing is anyway short lived as was evident from the Bijoy-Ishwari tussle about the pregnancy and the baby. Since beginning Dev and Sonakshi have never projected themselves as a team to Ishwari; they have been trying to allay her fears it independently; so neither the family nor Ishwari view them as a couple. Their biggest hurdle in their relationship is themselves; even before the break-up they never worked as a team to win over Ishwari because of their contradictory personalities and the aftermath of the beak-up has only compounded these differences. So Ishwari continues to be in control of their lives and relationship. Once the truth of false pregnancy is out, Ishwari will empathise with Sona because she knows this mess is as much of her making as Dev's. This might finally be the trigger that will get Sona and Dev to open up to each other especially now that Ishwari's issues ATM appear to be gone. Honestly I've had my quota of angst and drama with the break-up and its after math so hoping now we get to see some romance.