Probably the best way to find what she's looking for is at the local public library.  There you and she should find a wide variety of picture books, as well as informative handbooks, showing flowers, arrangement
styles, color combinations, etc.  The library is great, because they have very expensive books that most brides would never spend the money to own forever, but you are able to use and enjoy them only for the time that you need them.

A reasonable-sized retail bookstore will also carry a number of different floral titles.  Which are most useful depends on what you wish
to get out of the book. It's best to look through several and see what seems to address your/her specific interests and needs.

However, one nice general interest book on flowers and flower arrangement is the Reader's Digest Home Handbook of Flower Arranging.
It contains photos of specific flower varieties separated by season, floral arrangement ideas and suggestions, floral arranging techniques,
as well as a broad text listing of flower varieties with information about color ranges, seasonal availability, uses and specific arranging needs.  I bought this book a few years ago and find I refer to it quite
frequently.

Best wishes to you and to your friend.
Foreverwed.com expert-- Sara L. Ambarian
author of "A Bride's Touch: A Handbook of Wedding Personality and
Inspiration"/ creative consultant/ custom bridal designer
mailto:sara@www.foreverwed.com
For more wedding information:
http://www.foreverwed.com/~sara