Best way to show great gratitude.

Recently a Chinese girl found out that I was homeless well attending a different college then she does. She offered to let me stay with her. In order not to intrude on her room mates space I sleep on the floor of her bedroom. I have offered her payment three times and she has refused all three. I have ordered two gifts that I am sure she will like and read about the etiquette of gift giving but still am missing a component. What is the right approach to explain how grateful I am with out making her uncomfortable? Also I do not know the proper etiquette for being a good house guest. So how does one behave as a good house gust? How does one express best express gratitude with Chinese etiquette?