"The sun hadn't quite set, but in the darkening sky, stars had begun to appear around Talns Scar. The Tear hung just above the horizon, a star much brighter than the others, named for the single tear Reya was said to have shed." ([Words of Radiance] Kindle Edition, pg. 362 of 1080)
Since we know the names of all the Heralds, I can only surmise Reya is Cultivation's real name and that the tear she shed was when Tanavast died.
Reya is somebody female and important.