I don't think anything wrong with your email. Since she knows

that you are Chinese, and she called the products made in China "crap", that is just plain rude. Once one of my co-workers said that in front of me about it, and used the same words, "crap", I told her, if you do not know the whole story, do not talk about it, and call it names, if you do not like the certain food produced in China, spend more money to go to the high end grocery store, and get the fancy food.
Most of people will be careful to talk about these things in front of me since I am Chinese, for those who have throw the careless words like that need to be told how to be considerate and polite.