Naina...Topper Naina is probably suffering from amnesia.
I agree my understanding of the characters is from reading the LUs and analytical posts here,but I can not help assuming Naina has amnesia given her cold reaction to her husband's pleas to not abandon him like his mother...
Naina who first said said the truth which resulted in Sameer's rustication and then lied to save Sameer cause she did not want him to be rusticated again? It showed she learnt from her mistakes...
Naina charged him for the paper-stealing incident labelling him a thief infront of all,making him lose even the little bit of attention he ever had from his mother.And after knowing the real culprit she chose to keep the truth hidden.It reflected on her love for her family.
But then she tried her best to befriend Sameer again.In the process,coaxing her best friend to give up on playing the lead in the play and ending up playing the sipahi.She also convinced her teacher to go for a boat-ride on the school trip...She did not pester her Chachaji to allow Preeti for the trip,maybe cause she wanted some lone time with Sameer and probably Preeti would have been an hindrance...So very typical of a teenager in love.
She wove a sweater for Sameer thinking it would assuage some of his pain of not having one from his mother...She took Sameer's words literally and burnt her hands to feel his pain...She could sense his inner pain and yearnings.
She allowed a guy in her room at night going against all societal norms of that era...It showed her courage to stand up to a situation.
She could sense him in trouble even when distances apart.She did not understand his anger when he just threw that photo without any explanation and yet she was worried to death about his safety so much so that when he called from Delhi all she could ask was whether he was fine and had reached home.She failed in her exams and topped yet again after a promise given to Sameer.She plotted to send Mundit to Delhi and even tried her hand at dancing, a hitherto unknown territory for her,just to go to Delhi herself.She sensed Sameer's presence back in her city and tried bringing out Sameer from his manhoos phase.She even tried smoking to get Sameer to talk to her.She agreed to the movie date as well as birthday date being fully aware of the consequences if caught.She denied Sameer from accompanying her even though it was almost 11 in the night when they reached her home from the police station.It all showed the depth of her affections.
She broke up with Sameer on Shefali's advice and then agreed to marriage with another guy.It somehow reflected her deep sense of gratitude to her Chachaji for bringing her up like his daughter,but the she was shown as someone easily swayed by other's words unlike the school Naina who believed in her feelings for Sameer.
She pounced upon Sameer the moment Chachaji gave his nod.When Munna's promise became a impediment,she pulled off a jumping-from-roof stunt just to get back Sammer being fully aware that Sameer would definitely come after her.She did not even have a word with her proclaimed best friend before cancelling her nomination and putting in her own candidature.And when Swati tried to have a word with her she was too absorbed in her own world with Sameer.This did display a streak of selfishness in Naina unlike the old Naina for whom it was family and friends first.
She not reciprocating to Sameer's intiation of intimacy was fine given her orthodox upbringing,but then claiming that she had done equally for this relationship when the engagement almost got cancelled seemed odd given in school she knew exactly about her own capabilities.
She being unable to convey to Sameer about the hair fiasco throughout the marriage ceremony resulting in him being angry when it was revealed in front of all,jumping on her marital bed being fully aware that Mami was on her trail like Karamchand jasoos,being angry on Sameer for not supporting her during the hair revelation and questioning him "yehi tha tumhara pyar",being totally ignorant about intimacy even after her Shaadi-ke-baad rant throughout college,not acceeding to even a single damn kiss,suddenly being unable to dress up according to the occasion even though she used to take care of her looks both in school and college,incessant arguments with Sameer in a one-upmanship game,abruptly transforming from a Swacch Bharat volunteer of 90s into a careless snob without any concern for the filth and dirt around and threatening to leave the marital home at the drop of a hat without a second thought as to where would she go cause quite clearly hers was not a family to accept her back at home...Baffling!!! Isn't it?
So all I can think of is probably she is suffering from amnesia...