The disagreement started once we saw all those new Olive Garden commercials doing it. Her point is that nothing is going to taste great with the same thing used twice in a dish. I say differently. Like if you add a good Italian sauce or something and use rigatoni noddles.
There is nothing inherently wrong about that. Maybe what your mother is getting towards is that maybe you should cut the amount of noodles in half if you want to add potatoes, otherwise you will just end up with too much.