What is she doing?就是独立的疑问句,问句里be动词（这里是is）要提前.
“What she is doing”一般放在另一个陈述句或疑问句里,例如You gonna tell me what she is doing.或者Could you tell me what she is doing?
这种时候就要把提前的be动词（这里是is）放回原位也就是主语的后面,所以变成what she is doing