Portugal and Spain have the bless of having a very diverse genetic pool, after being invaded by many, many, many people over the millennia.
Also, due to the expansive colonization of every continent by both countries, I would bet that all human genomes can be found in the Iberian Peninsula. France, having a frontier with Spain and also being a target for emigration from either of the Iberian countries, has a very large Iberian presence.
So, why even assume it is a Mexican? Because that is your reality I suppose. Mine, being in Portugal, I would assume she's from the South of Spain. And yet, we can both be wrong and she may very well be Venezuelan, Chilean, Colombian or any other country in South or Central America. Even Mexican.........
Migration is a phenomenon that happens EVERYWHERE. Not only to and from the US. Yeah, hard to imagine I guess.
Peace