I think this one is particularly difficult to answer. I mean, to put it simply, it depends....and it depends on everything. First of all, if it's such a thing as they just don't get along, that's pretty simple. Don't hang out all of you all the time, and maybe over time, everyone will start to get along. It's a good theory, I know...who knows if it would really work.
However, if it's something like moving some distance to be with your significant other and it is away from your friends, then it is more and less complicated. Which is, I know, awesome. Here's how I see it. Right now, I am contemplating moving to another country for my significant other. Yes, I would be away from my friends, my family, everything familiar, everything that I've known. But the thing of it is, that right now, it's not home because it's not with him. I know that sounds terribly sappy and trite, but it is how I feel. I would and/or will miss my friends and family terribly (at least...I will miss most of my family), and I'm not discounting that, but there is a time in life where you have to go out on your own....really out there. Stand on the ledge and look over it...and then take that leap of faith. If your friends and family love you, they will miss you terribly, but they will let you go, knowing you're never really gone.
I guess what I'm saying is....if your friends are the friends you believe them to be, you'd never have to choose between them and the person you love. They would back you up, they would miss you, they would love you, but they would want you happy.
And also, real friends and significant others wouldn't make you choose between them.
If you're wondering, he makes me very happy :)
My two cents...I'll get off my soapbox now.