It's not as simple as "Which is more important, partner or career?". When both people have careers that they value, both people in a relationship have to make some (carefully weighed, ultimately balanced) compromises.
While you make a good point, the problem is is that these decisions are rarely carefully weighed and balanced.
In this case, what the OP's girlfriend is probably asking herself is, "What's the best program that I can get into?," and probably assuming that the relationship stuff will work itself out. (Granted, these are just assumptions, but that's what it sounds like his girlfriend is asking herself.)
But there is a VERY good chance that, 9 months from now, she will realize that she
ought to have been asking, "Which situation would I rather be in - an excellent program that ultimately jeopardized, or at least severely strained, my personal life, or a mediocre program that allowed me to continue my current relationship?"
And what makes a program "sub-par"? Is it truly malignant, or just not as good of a "name" as another program? One of the things that has surprised me the most about interviewing is that there is no hard-and-fast definition of a "good" program. In the field I am interviewing for, there have been people matching into extremely difficult fellowships from no-name programs. There are people at traditionally malignant programs who have fulfilling personal lives, and seem honestly and truly happy.
But if the local program really is subpar, asking/expecting her to take it is asking for a lifetime of resentment from her.
True....but the resentment flows both ways.
If she goes to a program that is 6 hours away, expecting
HIM to take it might be asking for a lifetime of resentment from
HIM. There's no reason why he won't start asking, a year from now, "If you had been willing to make a sacrifice or two and go to a program that wasn't as good, but was only 2 hours away, we might actually see each other once in a while!" So, who knows?
OP: LDRs are not fun. Sure, sometimes they work. Sometimes they work very well. But, fundamentally, it is a big emotional shock to go from seeing this person every single day to seeing them once every few months. Suddenly, the person who was there for you at the end of a long and tough day isn't there anymore, may be inaccessible by phone/internet, and that just ADDS to the frustration. No one here can tell you whether or not it will work out, but it will probably not be an easy road, no matter how it ends.