You bring up an excellent point. My great-grandparents came here in the early 1900's from Italy. My father told his grandpa when he was still a kid 'we in American now, you speak English!'  I laugh at that story when my family shared it with me. 

We come from all over the world to the US, but fitting in, speaking the 'general tongue' I think helps us communicate and stay connected. I don't care where you come from, but your actions, your behavior and how you talk will be watched and even judged. IF she was here since then, she picked up on the language. Some of them like to play stupid and for that, I say send her packing.