You are a green card holder and will be applying for a US citizenship If you married a Chinese citizen who is living outside US and then apply for the citizenship together will she become a citizen?

She can get US citizenship right after the marriage. You'll have to get her a fiance visa and start the Immigration process. After obtaining her green card (which usually takes about 2 years), she needs to live in the US for an additional 3 years. Then she can apply for US citizenship.