I think today, it showed how much she still loves Prem and how much she still thinks of him. When Chahat left with her teacher and she was thinking of how Prem would be so proud of her for raising Chahat so well, it made me think, deep down in her heart, she really wants Prem in their lives. She wants him to see Chahat's accomplisments. She wants Prem to tell her what a great mother she is to their daughter and maybe those feelings always came up in the last 6 years whenever Chahat did something new or great. Deep down, she really wants Prem to love Chahat and be proud of her like she is. But than she remembers everything and tries to push those thoughts away and try to convince herself that she doesn't need Prem in her life. When she was thinking of how proud Prem would be, she had such a geninune smile on her face and she seemed truly at peace and happy but than everything came back to her and that smile went away and more than haterd it was frustration that took over her face.
Saying that Additi Gupta is a fantastic actress and I love how she uses her expressions so perfectly to convey her feelings. Her eyes and expressions speak more than her words and that's truly a sign of a great actress.
Also I loved Chahat and Heer's little conversation when they were walking to school. Anyone that have any doubts that Heer never shows Chahat any affection should change their mind after this. It's clear that she absolutely dotes on her!