她在吹长笛用英文怎么说

“她在吹长笛”用英语可以说成 "She is playing the flute."

"Playing" 这个词的意思是“演奏”，可以用来描述她正在吹长笛的动作。例如：

She is playing the flute beautifully. (她正在演奏美妙的长笛)
He pstened to her playing the flute. (他在听她演奏长笛)

"Flute" 是英语中长笛的意思，是一种管乐器。