Mikki,
If you look here on the Oprah website, these are all of the past book club selections. http://www.oprah.com/obc/pastbooks/obc_pb_main.html
However, non of them appear to be written by "two women", so maybe it was a book that Oprah liked but it wasn't a book club selection per se.

Also, this is a list of Oprah's favorite books: http://www.oprah.com/obc/favoritebks/obc_fav_main.html