Dana Hall has around 20% international students. So if you factor in the students from Hong Kong, Korea, India and Japan, there should not be a lot of students from China. Most of the top schools have a large Asian population, but many of them are born in the States.
No, not a lot of students end up going to Wellesley. This is their matriculation list for the last 5 years: http://www.danahall.org/college_counseling/matriculation_list
Dana Hall sends their students to some of the best colleges in the country.
Dsna Hall's tuition is on the high side, possibly because it is a smaller school.
You might want to know, just in case, that Dana Hall is an all girls school.