According to some forms of Kabalistic doctrine, the letters of the Divine Name—YHVH—correspond to the Sephiroth after this manner:
Y = Chokmah (Father)
H = Binah (Mother)
V = Daath (Son)
H = Malkuth (Daughter/Bride)
As the story goes, in the beginning the Vau and the He Final were united in a state of marriage. This could be the
first marriage of the "Prince no longer of this world;" By an act of Divine Providence, the He Final was exiled to Malkuth where she resides to this day. This is the so-called Fall. At some point in the future, also by an act of Divine Providence, the Vau will raise the He Final and once again Paradise will be restored, the
second marriage of the "Prince."
If this is what Waite's talking about, the High Priestess must have a role in the Restoration, but I'm not exactly sure at this point what it would be.
Waite adopted this Kabalistic doctrine and wrote about it extensively. Once again I'll post a link to his diagram from
The Holy Kabbalah as it illustrates all of this.
Tree Diagram