Who is Kareen Birkman from Johnny Got His Gun and what is their importance?

Kareen Birkman is Joe Bonham's beautiful nineteen-year-old girl friend in Los Angeles, California, at the time he is drafted into the Army, Kareen Birkman insists she is not a "mick" but a "bohunk". She begs Bonham not to report for duty after being drafted. As he lies in his hospital bed, Bonham remembers their brief time together and their plans for a family, and realizes this is no place for him, no war for him, none of his business.