I know we have discussed a lot on how Dev was responsible for the marriage failure. I want add my two cents on Sona.
What I have understood about Sona's character - she is exactly like Dev, that she also gave first importance to her own parents. Dev/Sona were never worried about themselves, if someone were to hurt them. That is why Sona was okay with Mami's taunt and Dev with Bijjoy's taunts. It never affected them. But when it came to their parent's family, they were more cocerned - saying "My family", "My baba" , "My maa".
We saw similar kind of situation before their first break up too. Dev and Sona had a fight over their parents when Bijoy visited their house. Sona was complaining that Ishwari insulted her dad and Dev defended his mom that she would never do that.
Have we seen any episodes after their marriage, were Sona was complaining to Dev about Ishwari or Mami or anyone. She was upset with Ishwari for not considering her as part of the family. She always behaved well infront of Dev that she always loved Ishwari as her own mom and never had an issue with her. Dev knew it all along that Ishwari always considered Sona as an outsider. That is why he was happy to see their bonding after Sona's fake pregnancy.
Sona actually started complaining to Dev about his short term solution and keeping both mom and wife happy when they were in Shimla.
When slapgate drama happened, Dev constantly reminded her about their promise about working together and asked her for direction what do next. This is when Sona started saying "My family" and "My baba" and "your maa" again.
I agree Dev lied before. He hid her medical condition, her pregnancy results. But for whom? There were no selfish motives there. He did for Sona.
Dev taking help from his mom and hiding it from Sona, I don't consider that as a big lie. Sona also hid her business venture with Dev. Did he ever complained why she lied to him?
I remember Sona once told Ishwari that she knows Dev better than anyone in their family. Sona knew how Vicky was. She also knew how mami is. She had seen her stealing money from Ishwar's room before their marriage. Problem here is she trusted a cheater Vicky over Dev. Why? Because she was angry with whatever happening in her life. That could be her family's pride, her infertility issue...
We don't know the real reason behind the hurtful words Dev used; whether it was intentional or said in anger. If I think logically or go by Dev's character, he will never say those words to her even in anger.
Dev and Sona had a fight before too. Even in Shimla, they were fighting and saying to each other why did they marry each other. All couples fight and move on.When we fight we say rude words..sometimes use words that hurts yourpartner though we don't really mean.But do you break your relation just because of that. I don't think so...
I will add the final words from Suchi's analysis - Sona loved Dev but lacked the trust & commitment needed to keep the relationship alive. She was not open to discuss things more rationally. Just followed her's parent's pride but failed to respect her own husband's feelings. She was daughter first, just like Dev.