Ultimately, you need to do what is best for you in the long term. I totally understand your debt concerns and I have similar doubts about which school to attend. I don't think you should feel obligated to choose ND because they accepted you, especially if it means jeopardizing your long term goals.
+1 taking on debt is something that everybody should think about, especially when you have the opportunity to go to a closely ranked school without incurring any debt (or any more debt). Do what's best for you and best of luck!