The Chinese media (or rather her PR machine) was at one time touting LYF as the most beautiful Chinese actress in the last 50 years, which is kinda stretching it.
I think the ethereal quality came to be associated with her because of the characters she played early in her career - Wang Yu Yan, Xiao Long Nu, Ling Er. She looks like your typical girl-next-door in recent roles, e.g. Love In Disguise with Leehom Wang.
Actually, I think Barbie Hsu is much more beautiful than LYF. Just my opinion