Like Sayali said above me, she is very aware of people, i've noticed a few times she guesses what the others are thinking with Nikhil several times and also with Barkha, so as sensitive to other's feelings as she is, she would not have gone out of her way to embarrass the family and because Nikhil doesn't know his wife too well because even when he is with her his mind is elsewhere, thinking of his love Ishana and the problem he is in between two women so his mind is not taking in Laajo's respect for others.
Nikhil was only too aware of Barkha's trap and didn't want to give a whiff of an opportunity of that plan to take place. So I'm glad that Barkha and Ayesha's trap with the broken sandal wasn't allowed to come to fruition.
Another reason I don't mind that Nikhil didn't take Laajo to the party is I don't want Laajo to forget that Nikhil does not love her and loves Ishana because she found out a day before about this and had he taken her to the party introduced her to their society as his wife she would rely more on him completely but here this guy only helped her at the village with her family and neighbours, so if she is serious about studying to be a doctor she should be thinking about taking her life in that direction and not settling down with Nikhil as a housewife because it's clear he doesn't want that relationship with her and his family don't want that from her either. So this what has happened should make it clear to her where she stands in her husbands affections and she becomes less dependant on him.