As we know that for every action there is equal and opposite reaction
So here it says that if we apply some external force on a system then system will exert same magnitude force on us but in opposite direction.
This is Newton's III law which is applicable in all classical situations
Now here we can see in the given situation we have given that Trinity pulls the rope with her weight so As per Newton's III law the rope will Pull Trinity by same force i.e. equal to his weight in opposite direction.