U have to see the thought process behind what choti sumo said , her words were forget shravan and u just have nanu , which is pointing to the upcoming story where Suman has to forget shravan and will say yes to Adis proposal due to nanus health , she will just remember that nanu is the only family she ever had and will try to keep it that way by making him happy . So the words u thought shouldn't be said or are selfish are actually not they are pointing towards to the path of upcoming story ..