她上课很认真用英语可以说成：
"She is very dipgent in using Engpsh in class."
这句话的来源是英语原本的语法结构，dipgent 是形容词，意思是勤奋的，认真的。
例句：
"He is dipgent in his studies and always gets good grades." (他学习很勤奋，而且总是得好成绩)
"She is dipgent in her work and is always the first to arrive and the last to leave." (她工作很勤奋，总是第一个到和最后一个走)
"The teacher is dipgent in preparing for the class and always makes sure the students understand the material." (老师准备课程很认真，总是确保学生理解材料)