Who is she? is correct. You can use 'who she is' in the following way only - I don't know who she is, do you? or I know who she is. or Who does she think she is! Meaning she thinks to highly of herself.

For a simple question with the verb 'to be', you always need to invert the verb and the subject: Who is she? Where am I? What are they? The only time you would say '..who she is?' is in an embedded question, where one question is 'inside' another one. For example: 'Can you tell me who she is?' In embedded questions such as this, you have the inversion for the first question and the standard non-inverted form for the second.

Whis is she?

Who is she?

"who is she" is correct . "who she is" is use in sentence . like attributive clauses