क्या "Where is she?" का प्रयोग गलत होगा?
No. It would be correct to say "Where is she?" for वह कहाँ है?
IMO, in the given sentence, someone is asking where is she at (in reading a book, writing a novel or may be some other ongoing process).
I think से gives meaning "from" instead of at. से is also in suggestions.
is it also correct to say उसके पर कहाँ है ?
Where at she
B to ho skta h
वह कहाँ पर है