What nationality is Sylvia Lea Burton supposed to be?

The Jayne Meadows character, a former love interest of the brothers. When she is talking to Hepburn in the latter half of the movie, she says to Hepburn, "Before you went to war in this country, you went to camp, didn't you? Where was Mike all that time?" So if the U.S. is "this country," what country is she from? She sounds American to me. (In glancing at her bio it seems she was from China. Did she incorporate this into her character for no reason?)