Dear Lily,
It's very kind of you.thanks very much for taking care of my father these days.
I was busy finishing my project and when my father was ill ,I had no time looking after my father.my mother was too old to look after him .And she even can not look after herself.And when I was in trouble,you helped me with no regret .I was very happy to be your friend.you are like a real friend.when friends are in trouble ,you give a helping hand to us and try you best to help us.in the future ,if you have any problems,please tell me ,I will try my best to help you.
to show my thanks ,would you please come over to my home whenever you like.my father and my mother also want to thank you .my father told me that you are a good kid ,he want to have a dinner with you .would you like to come?before you arrived,please call me ,we will welcome you .
thanks very much
yours sincerely
Mary
（额……写死我了,我刚开始写了一次,不小心给全删了,又重写）