Who is Shevaun Tillman from Tai-Pan and what is their importance?

Shevaun is twenty and one of the eligible ladies in Hong Kong. She is the niece of Wilf Tillman, the American trader. Her father is a senator from Alabama. She is nineteen at the beginning of the book. Her family wants her to marry Jeff Cooper, but Shevaun is interested in Dirk Struan once they learn his wife has died. Even though Shevaun is engaged to Cooper, he sends her back to America to think it over for a year. She has her eyes on the Russian archduke.