Ohio State or Notre Dame for Mathematics degree

tOSU’s in-state list price is $25,820, according to https://sfa.osu.edu/incoming-freshmen/about-aid/financial-aid-eligibility . The Maximum scholarship is $5,000, according to http://undergrad.osu.edu/cost-and-aid/merit-based-scholarships . So the net price should be $20,820, which means that your original estimate of ND’s price being 4 times tOSU’s price is a little high, since ND’s list price is $69,395, according to http://financialaid.nd.edu/cost-of-attendance/ .

Did you try ND’s net price calculator to see an estimate of its financial aid? In any case, you presumably want to wait for the actual financial aid offer before deciding.

But you need to figure out what your actual price limit is for her college so that you can still afford to contribute fairly to your later kids’ college costs, in order to avoid future family conflict over any perceived unfairness if your later kids have tighter financial constraints on their college choices due to overspending on your first kid’s college. Once you figure that out, you can know whether ND is possible once it delivers an actual financial aid offer.