In earlier ages the same picture we could see in more local case when man or almost always girl was need to move from one village to another one or from one region to another where our girl doesn't know anyone excepting her new husband his family(parents) etc. And nowadays we can face with almost the same but with that difference that now it can be another country or even different part of the world.
Of course it's your cousin choise what to do but the best way will be to support her decision and help her not to be lonely.
Or maybe to try talk with guy and help him ho learn beter language and culture...