To some extent, I understand Preeto's concerns, but she is overdoing it. Even if Heer had had no physical problem, nothing could have guaranteed a completely happy marriage, if there is such a thing.
Even when two young healthy people get married, who can tell what the future will bring? One can meet with an accident and remain paralyzed for life, what should his partner do? Leave it to his faith? Virat's bhabi, apparently, married a perfect man, and it turned out he is infertile. Harman and Saumya managed to adopt Soham and yet the fact alone of becoming parents couldn't save their marriage from sinking. Preeto herself was thrown out of the house by her own husband so he can live peacefully with his mistress. There is no such thing as a guarantee for a happy married life.
And about society... society will always have something to complain about, sometimes they just pick on others to run away from their own problems and their own imperfections.