Thanks so much for the terrific response.
So, it sounds like Denison, Purdue, (And, I think it's safe to say, U of Cincy) are all rigorous. So, any will fit the bill.
So, the tie-breaker would be comfort (she likes Purdue).
Perhaps I'm worried Purdue is rigorous to the point of being harsh. (grade deflation)
fwiw:
She has an absolutely stellar work ethic. As a shy person, she is unnecessarily, but too-frequently intimidated by professors. (she doesn't speak up in class, rarely answers a question...). But gets her A's and a few B+'s based on putting in the work, every single day.
I really thought she would prefer a small class size, but, not so. She prefers being anonymous in a large class; she's fine one-on-one i.e. labs will be no problem.