Who is Mary Wilson from A House Divided and what is their importance?

Mary Wilson is Mr. Wilson's daughter (Yuan's teacher). She is described as serious, witty, and reserved. While Yuan is in America, Mary's family invites him to the Christian church in the hopes of converting him. Yuan quickly learns that Mary does not share their faith, something that endears her to him. While Yuan is in America, he and Mary play at romance...... meaning they each seem to be romantically interested at different times...... never at the same time. In the end, they finally kiss, something that surprisingly leaves Yuan revolted. Their relationship thus ends.