When Arjun stole keys and question paper, created huge rift between Samiana and the bet thing followed. Which made Sameer fall for Naina.
When Arjun initiated fight with Sam, after knowing about the bet, it ultimately created misunderstanding and difference between Samiana. But it was followed by the decision of Rakesh that Sameer will take care of Arjun and which ultimately strenghten the Samiana love story.
And now, his affair with Shefali may create some distance between Samiana but I am hopeful that the moment Naina will be out of this Sefjun storm, she will again become the old Naina who will balance between chachaji's expectations and Sameer's love and I am expecting something beautiful which will make Samiana's relationship more close and more strong.
As at the beginning of the Samiana re-union in college, the voice over of Naina told that, "college ka safar bohut haseen tha and issmein har tarah ki masala tha", then I don't see any huge break-up, it will be ok after initial hiccups.