I've actually given your situation some thought because I've recently just broken up with my gf , partly because i'm going away, 2000 miles+ away, for school. CA to PA!
Why is the school your dream school? What does a "dream school" comprised of? Its rank or prestige?
Since you and your gf (im assuming someone you truely love) both got into a TIER 1 school, it's good enough as is! You will make as good of a doc as any other. Hence, I would go for the same school as your gf because it will definitely make the relationship better. And 80miles will definitely be a long distance, on top of going through med school's work load, seeing each other over the weekeend might not even be an option for some time. Maybe go over to study together? Honestly speaking, you going over won't be all studying. It'll be because you want to spend valuable time (non-work related)with her, i mean you've already studied all week! Truthly speaking, you'd want to go over to get "some". So studying will partly be an excuse. What i'm saying is that by going to the same school, you both can study together on the weekdays and go out on the weekeneds if it allows. Most important is that you AND your gf's schedule will be synchronized.
Speakin from experience, having gone through sort of a long d relationship of 80miles roundtrip myself, it would definitely jeopardize the relationship. Possibly even academics if an argument occurs because nothing's worst than leaving an argument hanging because solving the problem over the phone just doesnt cut it. I dont know about you, but alot of times i had to go talk face to face to mediate the problems.
Now, all of my BS would only apply if you truely want to spend time with this ONE girl, if you know what i mean..... 😱