depending on their living circumstances, they'd have a much easier time in the EU than the US.

In the EU "human rights" extends to the right to respect for private and family life[1], meaning that there are much different rules on unmarried partners than in the US.

[1]: http://echr.coe.int/NR/rdonlyres/77A6BD48-CD95-4CFF-BAB4-ECB...

Don't necessarily have to go back to her country.

ahah that's funny I'm myself from a EU country. Although I agree with the fact that there's plenty to do outside the US, we are not willing to relocate because we come from different countries and we would experience work authorization issues elsewhere as well.