I think the mother is just worried.. its understandable that shes nervous since namwoo is so much younger.. the mother doesnt know her so of course shed be worried that perhaps since shes young, shed have a change of heart or smth.. obv she wants her son to be happy but also in a healthy relationship)) im just hoping that thats the case and once she gets to know her, shell warm up to her.
Oh I already love the brother !!!!!!