I don't actually know a ton about Valpo, other than it's a smaller school that quite a few people from my high school class went to (10 out of 790, so...). Seems to be a very nice campus, good reputation, close to Chicago.
Now that I'm reading this, though, I really actually have to second Iowa State. My dear friend from birth was a Gamma Phi there (as were two other girls from our high school class)
. The advisor for my sorority's chapter here went there, and she is someone I admire greatly. Everyone I have met from our chapter there is impressive. My sister-in-law's sister went there too. To a person, everyone I've met who went there, or who has a child who is there currently, just loves it. The academics are excellent, you don't have to be Greek, but if you want to, the opportunities are wonderful, and it's "midwestern casual." I think it's big but can be made small enough---I've never heard anyone complain that it's too big.
My brother went to Purdue; it sounds like he was a lot like your daughter. He was in the engineering program, and not Greek, and it was a wonderful experience for him. Definitely worth considering!