We saw different shades of Sameer this week. During pooja didi's wedding Naina' VO said that Sameer very well knew which of his words hurted someone's feelings and which words touched their heart. I feel this was what was shown in this week's episodes. He very well knows how to break someone's heart and how to win someone's heart. But the truth is he can't see Naina heartbroken or sad. He still feels her pain even though he doesn't express it.
He is trying to hide his real feelings for Naina. According to him Naina left him and he feels that Naina betrayed him. Though i dont totally support him but he is not completely wrong in thinking like that. Its his frustration that is showing up. He wants to call Naina bewafa or selfish and pretends to hate her though its exactly opposite to his true feelings. He is not able to accept that he still loves her no matter what. He wants to get a mental satisfaction without any conflicts in his mind. Hence he is masking his true feelings with exactly the opposite feeling. Though deep inside somewhere he is still aware that he still loves her but doesn't want to accept that fact.
This is just my pov your pov might be completely different from mine. I do not entirely support Sameer or Naina both are right and wrong in their own way. I only support Samaina and want to see them together.