Georgia Tech is incredible for mechanical engineering.
Assuming she gets no financial aid, Georgia Tech would be the way to go if she lives in Georgia. If you are out of state or incredibly rich, I would go to Cornell.
It isn't really worth it to take out $50,000+ in loans for an engineering undergrad degree. If she made it into Cornell undergrad, she will probably do fine at GT. If she does fine at GT, she'll have a great shot at Cornell for grad school, where it really counts.
/From someone who came to grips with reality and Choose Michigan debt-free over Cornell and $100,000 in loans.