The implication of the moon being beneath her right foot indicates a notion of subservience on its part and dominion over it. Ghilan'nain is indeed depicted, by contemporary Dalish lore, as having hair of snowy white. In the older tales hailing from Arlathan per Inquisition, Ghilan'nain was not made into the first halla but was instead the creator of them.
Andruil is a likely person to be depicted here. The hare is a very sacred animal to her -- along with the owl, which IIRC the owl is also shared with another god -- and it's entirely possible it's meant to depict Andruil in a way meant to convey she and Mythal did not get along (since Mythal created the moon).
But I've also always thought that it was Ghilan'nain and was meant to symbolize the relationship between the two -- Andruil and Ghilan'nain -- because IIRC it was rumored that they were lovers. But my memory might be playing tricks on me.