Translation Consternation

(My mom prides herself in knowing English pretty well, even though she is not originally from here. She’ll speak Spanish to us, but not to others. My mom is currently speaking to me in Spanish while we are sitting at a restaurant.)

Waitress: “Hello, what can I get you to drink?”

Me: “Coke please.”

Waitress: *to Mom* “Que quedes tomar? Agua?”

Mom: *frosty look* “DIET COKE, PLEASE!”

(The waitress looks shocked and scuttles away.)

Me: *mortified* “Geez, Mom, you were just speaking Spanish to me! Don’t think you that she was just trying to make you feel more comfortable?”

Mom: “I don’t care; we are in the USA! We speak English here! So anyway…” *continues in Spanish*