要看你想跟她说什么了,下面我举个例子,说你想更了解她的生活,爱好等.
Dear XXX(名字),
How are the things going on with you?
I am XXX,I know you from my uncle(你对你美国亲戚的称谓).And I am really willing to have a deep understanding about your favorites and your life in the US.Do you want to share the matters with me?Now,there is a summer vocation in China,and I want to ask you about your plan about this summer.
I am expecting your reply.
Best wishes
XXX