I don't know who/whom she is.口语中可用whom,正式的书面语用who.宾语从句中是陈述句语序即:主语+动词+其它.
I don't konw who she is
who后面是个从句(相当于单独句子),要现有主语再加谓语吧?she是主语,is是谓语
I don't know whom she is.
whom是she is 的宾语,用宾格
I don't konw who she is
who 引导的宾语从句要变为陈述句语序
I don't know who she is. 定语从句在否定句和疑问句都要用陈述句语序。