raj has done many good things to her. but he committed the grave mistake of hiding a very big truth from naina -he killed naveen. and to naina this comes as a shock b'coz raj is the only person in the world she trusted. she has even begun to fall in love with him and that makes it more difficult for her to handle the situation.
naina is not perfect. she behaved exactly as expected. it will take some time for her to accept this harsh reality.
raj is not perfect either.
i would say naina and raj r undergoing a difficult phase. it is upto raj to win back naina's trust and he is the only one who can guide her. whether naina deserves raj or not i don't know but i would say he is the most suitable and perfect partner for him. an impulsive girl like naina needs someone like raj to take care and protect her and teach her just like her brother used to.