She doesn't have one.
This explains everything:
link The link is from Stephenie's official website and says (and I quote)
"For those of あなた hoping to find an Eメール address または a way to contact Stephenie — I apologize. There is currently no way for ファン to get in contact with her. Stephenie is still much too busy to re-open her ファン Eメール または カタツムリ mail addresses. Also, I cannot フォワード, 前進, 楽しみにして emails. She is in the process of writing/editing multiple books, and I think we can all agree that we would rather that she spends her time 書く instead of 読書 thousands of emails every day."
