I never felt Naina is wrong rather I feel she fell weak in the relationship. She lost her confidence in herself after seeing Rakesh's and family's reaction. In traumatic state and in huge emotional termoil shefali's words was the nail in the coffin. It happened with Sameer when Dadi's words pushed him to break up with Naina for her well being as Naina is feeling now that it for Sameer's good. They both took one sided decision of breaking up but the reason is their immense love for each other.
Naina needed some time to get back to normal and Sameer needed some patience. Her trauma was huge and fear of loved ones death was made her think that she is more inclined to family. All she needed in this dark phase was silent support and time to come back to senses But thanks to her family who pushed her to the end of the cliff, her biggest support system is being paralysed she is at her emotional lowest. She is my sherni she will surely bounce back
Now come to my bachha Sameer . He is nothing without Naina. He can't even think properly without Naina. Rather he can't breathe properly without Naina. Due to lack enough oxygen supply his brain works abstructly and he started behaving irrationally. What he is doing now. When a baby can't see it's mom around it depends on nanny. Just like Sam is doing now when Naina mummy is not around he is looking for the alternative, that is Su the nanny. He is still a child at heart. As nanu realized that Naina is the girl who will nurture him through out his life.
Hope both of them realise that what they meant to each other and they are actually don't have a home in real sense. Together they will make a home for themselves.
NB: please cvs stop su crap and start their realisation process fast.