How do you know if a foreigner is really interested in you or if they are just seeking a green card?

What do you ever truely know about another person? If you've been friends for over a year, and she's never started singing the Star Spangled Banner or some other similar song, and she's talked to you about living there instead of the US, maybe she's on the level. Why not? Do you want to live in Mexico? If so, go for it and see how that works out. But if you don't know yourself if she's being truthful with you, you certainly won't find any absolute answers here from strangers who don't know her at all, or you.