She's both, expat is just a term used (mostly by brits in my experience) to refer to people of British origin living abroad. It refers to migrants.
I see. In my part of the world, an expat is someone who took a job in another country. This country where they are currently resident isn't their home; they are merely there for the duration of their contract.
Expat is a word to distinguish white immigrants from the rest of the immigrants. White Americans living abroad are called expats as well.