By Dialects, Simple past

But I found many cases using "never + simple past" in Google Book search: http://books.google.com/books?lr=&hl=zh-TW&q=%22She+never+saw+a%22 , which has 676 results using key words "She never saw a".

Plain and simple, even though it exists in many/most dialects, using "never + simple past" is not Standard English. So you are limited to "she did not see" or "she had never seen", or some derivative of either.

References