How should I talk to my 9 year old girl (PDD/ NOS) about her
fondition? is there a book or a guide?

Here is a link to a site that has many good resources and a list of
books and videos that seem like what you are looking for:

http://www.autism.net/library/index.php

Here are a few of the books:

Andy and His Yellow Frisbee 
http://www.amazon.com/gp/product/0933149832/sr=8-1/qid=1152222917/ref=pd_bbs_1/102-3776410-7891324?ie=UTF8

Asperger Syndrome: A Guide for Educators and Parents
http://www.amazon.com/exec/obidos/search-handle-url/102-3776410-7891324?%5Fencoding=UTF8&search-type=ss&index=stripbooks%3Arelevance-above&field-keywords=Asperger%20Syndrome%3A%20A%20Guide%20for%20Educators%20and%20Parents

Overcoming Autism
http://www.specialneeds.com/books.asp?id=14006
 - More informative for Parents, but does speak to how to communicate
with your child about it.

Keisha's Doors - An Autism Story, Book 1
http://www.amazon.com/gp/product/1933319003/ref=pd_sxp_elt_l1/102-3776410-7891324?n=283155
 - Mainly for siblings of an autistic child.


Another good resource would be one of the support groups or forums
where others who have been in your shoes can give you good advice and
encouragement.

http://groups.msn.com/TheAutismHomePage/parentsupportgroups.msnw

Main Page: http://groups.msn.com/TheAutismHomePage


I hope that the information above helps you out.  If you require
addition information please post a request for clarification.

Thanks!

If you don't get any advice here, I suggest you ask the diagnosing
doctor, your daughter's school psychologist and/or school counselor.