The Sexually Dominant Woman: A Workbook for Nervous Beginners is a book that might be helpful. As best I know, it is focused more on basic understanding of BDSM and sample activities. I am not sure how much it discusses relationship issues. Books by Jack Rinella and Guy Baldwin might be worth thumbing through at a bookstore to see if they have the type of information they seek. Also, discussion forums that have more focus on lifestyle relationship issues might be useful to them.
Cheers,
Sea