Mao is not an Asian-American and obviously a foreigner from Gracie's standpoint. English is just a foreign language for Mao that she does not need to speak daily. I don't think Gracie would have said something like this if Mao was someone living in the US.
To me, if people living in totally different parts of the globe make jokes about one another's differences in a light-hearted way, it is perfectly fine. But if someone make fun of another living in the same community or country because of his/her accent, it's a totally different issue.