她画国画在班里最好．用英语怎么说？

She paints the best traditional Chinese painting in class
【or】She paints the traditional Chinese painting best in class
(都对)
(我的是对楼主的句子直接翻译，建议采用！谢谢！)

She is the best traditional Chinese painter in the class.
注：
traditional Chinese painting 就是 国画。

She does the best job in chinese painting in her class.

She is the best at drawing traditional Chinese painter in her class.