In Dev's case: Sona was insulted beyond limit, was questioned for her work ethics, was shouted at, had to face so much drama, yet when Ishwari came to know that Sona had made Dev wait, she never bothered to even reason out and assumed that Sona has so much pride! Even when everybody's intention was her health, her only concern was that her son's every minute is precious and how dare somebody waste his time. All selfish.
In Sona's case: It is Dev's bday, Sona wants to make it special, is excited more than she would be for her own, wants to spend some time with him so that he can be free to spend the day with family, yet when Asha will come to know that Dev couldn't make it, she will reason out with Sona to see Dev's POV and not be selfish with her own expectations. All unconditional!
So sweet :)