I would point out one thing that others haven't yet mentioned. Given that the two schools you are contemplating are fairly similar in the eyes of recruiters, a full scholarship can be a differentiating factor in recruiting. I can tell you for certain that a merit-based full scholarship is something that will make you stand out when recruiters select their candidates, and if it is a named scholarship it can also be a terrific discussion point during interviews. For example, my scholarship was given through the institute for entrepreneurship and that item on the resume was a great jumping off point for a variety of topics.
As 89nk mentioned, I had no trouble landing an internship with the LA office of a top firm. I also know that quite a few spouses have been able to find employment with Darden and the broader University. You might consider checking with Darden to see if they know of opportunities that might be suitable for your girlfriend (don't know if GF employment is as readily available as spouse...)
Finally, the most obvious question is, if you're admitted with a full scholarship and still don't want to go, why did you apply in the first place? I actually had a similar decision a few years ago (UCLA undergrad, LA is my hometown, admitted to Anderson). I understand that despite the popular opinion in this thread this isn't an easy decision, however I've been extremely pleased with my experience. I made the decision that I wanted a full business school experience, rather than just hanging out with my college buddies around LA. The money is definitely nice - and in fact I probably won't fully recognize how nice it is until I start working and think about the chunk of change that others must allocate to loans each month. For the time being it takes a lot of pressure of the job search and really gives the sense that I can be flexible if I want to, and with the economy as it is, that's definitely pretty nice.