Think I found what I was looking for. This page, http://www.hermetics.org/gd/GD-5.html
, near the bottom, shows a diagram from the GD Fifth Knowledge Lecture. Fire is in Chokmah and Water in Binah. As the elements are reflected down the Tree, Fire reflects diagonally into Geburah; likewise Water is reflected into Chesed and so on down the Tree. Air is in Kether and is reflected straight downward. This seems to be customary in the GD as it's found in several other places throughout their teachings.
Waite seems to have followed this, in the FRC at least.
"It represents Shekinah as the Lady of Reconciliation and Lady of the Pillar of Benignity, intermingling and reconciling the influences of Chesed and Geburah, regarded as cleansing water and saving fire."
As I understand it, "cleansing water and saving fire" should be taken as "respectively." The next quote makes it pretty clear.
"Fire of purgation in Geburah; holy Fire of judgment. In the name of transmuting Fire."
"There is a Water of the wise in Chesed. There is a Fire in the Water of the wise. That Sacred Fire is an influx from Chokmah. . ."
This last quote appears to be describing Water in Chesed which receives an influx of Fire from Chokmah through the path that connects them.