I haven't moved abroad, but am 23 and one of my closest and oldest friends moved away, when I was 14 and she was 13, to Australia. There was a lot of history between my family and hers (both of our parentshad gone to school together, etc etc) and we were more like family.
At the time it was absolutely heart breaking, and I remember feeling so utterly low, but we still keep in touch now, she has so many friends over there and would never contemplate moving back over here, and in fact tries to persuade me to go over there.
In fact, a few years after they moved over there my friend's oldest sister (who stayed in UK), and aunty and uncle and their children all moved over there too!
I think you should consider your daughter's feelings for sure, but ultimately, there will always be a reason not to go whether she is too young, has exams, just starting uni, or just starting a family, etc etc. I think you should seize the opportunity and do it now and I am sure she will thank you for it in the future :-)
Best of luck xx