Both schools are very strong. She is the one who will to have to attend classes, do the homework, and take the tests.
I don’t think that there is a bad choice as long as she goes to a school where she is comfortable. MIT is higher ranked, but that doesn’t make it a better choice for any one particular student.
When I was a graduate student at a top ranked university, there were plenty of other students there who had done their undergrad at schools ranked significantly lower than Duke, and one who had done their undergrad at MIT.
If it were me, and if my daughter preferred Duke, then I might try to get them to match MIT’s offer (although admittedly MIT has more $$ in the bank available for whatever purpose they care to use it).