Hi there, My family lives in the U.S. but will spend about 5 weeks in China this summer. We will be in Chengdu in June and July visiting family and friends. I have two children, 13 year old daughter and 10 year old son. I am sure they would love to make new friends. My son loves sports, plays soccer, basketball and flag football. My children and my husband speak very little Chinese, however. I speak Chinese and I am also from Chengdu.
Both my parents are retied English professors at Sichuan University, my mom tutored many students throughout the years. She might be willing to work with your sister.
Let me know if you are interested in meeting up.