Arfa, good question to debate.
Personally, I don't understand love at first sight, mujhe nahi hua, but I won't be as dogmatic to say that it doesn't happen to other people.
For me, though love can't happen in vaccum. Without a lot of scrutiny, good friendship bhi nahin hota mere liye, so love is out of question.
Here, what I felt is that Ruhaan had a strong attachment ( I don't want to call it physical attraction ) when he saw her for the first time. Probably, if they never met again and if he is simply left with pictures, may be that would have fizzled out or may be he would have made all attempts to find her again and pursue her, I don't know. But then, he met her in a very unexpected role and of course that led to disappointment. He didn't want to leave his chances of knowing her a little more closely by staying in her house. He experienced all of her moods, he also saw her underlying personality, almost childlike, fiercely protective of family, immensely responsible, a young woman trying like hell to be an adult and pull off a family and livelihood, a fighter. But he also saw a vulnerable young woman who is forever scarred by the cheater father and her rigid determination not to be the same. I feel all of this, probably his understanding of her true self, underneath that facade of a confident, cutting edge young woman, not what she is portraying outwardly made him gather all the finer emotions in her favor, eventually turning that strong attachment into unwavering, deep love for her❤️🤗. And then, from there on, one thing led to other and as they say, the rest is history😃He identifies his life, his happiness and his sanity with her. So, I don't believe even for Ruhaan it was love at first sight in a true sense, but what had turned into a love at first sight. I know he told us otherwise🤔and I don't know how to reconcile with that information. It is very sad that nobody, not even her family has a true understanding of real Mishti, barring Ruhaan🤗Bless them to be together forever❤️
Not sure if this makes sense.