She is Australia.还是She is an Australia.哪个对?还是都对?

She is Australian正解.
不可以用She is an Australian.
Australian指澳大利亚人.
如：
I'm Chinese.指我是中国人,没有a Chinese的用法.
如果一定要加冠词,后面要跟名词
如：
She is an Australian student.