Hi C.!
As a very involved college professor (I'm the prof who always ends up being a surrogate "Big Sister"), I can tell you that I see this VERY often - with my freshmen! The good news: When I teach the older set (especially juniors and seniors), I see this problem much less frequently. YES, most gals (and it always is a girl - my male students never seem to make this kind of judgement error!) really do "outgrow" this stage once they realize what college really has to offer.
The pattern that seems to be consistant:
1. Your daughter is probably worried about the relocation aspect. You say she's close to you; moving out of state w/o a friend in the world is scary. No wonder she wants to drag her BF with her. Someone is better than no one. She might already see her error, but her fear of being alone is greater.
2. From my POV, I would not encourage you to financially assist her in living off campus if she can get on-campus housing (even if it's not free, I would encourage you to tell her that you will pay for on-campus, but not off-campus, housing). Most of the opportunities to mingle with other students do not come in the classroom, but the dorm room. That's where she's going to see how her roomate has a GOOD BF and the descrepencies will become more obvious. And when her suitemate cringes after she meets your daughter's BF, all the better! Peer pressure can sometimes work to a parent's advantage in a case like this!
3. Don't lecture her, but if she asks for advice, give it. You are not obligated to support her poor decisions. If she wants to make adult decisions, let her recognize the adult consequences. College kids are very crafty in channeling parent funds to things Mom & Dad would NOT support. Most colleges now use ID cards that can be "loaded" with $$$ but can only be spent in places like the on-campus eateries, laundry facilities and bookstore. There are also usually different levels (my college has 3) of freedom kids can have with this $$$. Do a little research; don't load her card with the most "freedom-esque" level of funds. Local businesses like supermarkets and even clothing stores will accept these types of funds from kids, and my students always brag about buying beer! You don't want your $$$ going to stock his 'fridge.
4. Stay close with her. Take her shopping for dorm bedding - your treat. If possible, schedule a trip to the university - just the 2 of you! - to help allieviate her fear of the unknown (and when she sneakily slips in a flyer for an apartment, look the other way). Be the "rock" so that when this all comes crashing down around her, she knows that she can turn to you without fear of an "I told you so." College kids are so impressed with their "maturity" and seem to be very afraid of making their errors in judgement public knowledge. If she thinks she's going to be chastized, that might make her stay with him longer than she would have otherwise.
5. Some schools have policies with scholarship kids that prohibit off-campus work. Find out if that's the case, and sweetly make her aware. You want her on campus as much as possible. Even if she does opt for an off-campus apartment, encourage an on-campus job. It's nearly as good as a dorm, as she will be working with other ASU students and making friendships outside the classroom (ASU is HUGE; don't count on the classroom being her social outlet). Use reasoning like, "I've read that on-campus jobs are more flexible with your school schedule; in many cases, they pay better; you won't have to worry about the commute/gas prices; you'll make great connections with alumni, which can help you after graduation..." etc.
6. Most colleges host freshmen "camps" right before school starts as a way for them to become comfortable with the campus and know what to expect from their college experience. It's usually called orientation, and it might be available over the summer, too. Find a way to get her there, even if the plane ticket is pricey. Lots of bonding goes on (as that's the point) and, once again, her fear of the unknown can be reduced.
I wish you and yours the best of luck! College is a HUGE culture shock, so don't expect results overnight. She'll most likely cling to him through at least the first semester (assuming that he even makes it up there in the first place!).