Yes, Yash is not wrong at his place..
But he must have faith in her.. Why would she do such cheap things to promote one of her children..
For her as a mother everyone is equal and it was just a selection for the debate competition may be both of them could be selected.. Here there was not the case that one would win and other would be defeated..
Actually we know who did all these things but Yash don't know.. So, he is not wrong at his place.