Great !
i like the idea of an OGAM army with Epona
Very original one
She's listed in both the original rulebook and in the Celts supplement.
When I spotted her as an option I immediately thought of using the Copplestone Lady Godiva model I had lying around.
It did mean I had to source some horses (Irregular Miniatures Shire horses work nicely as shaggy Celtic ones) as Epona must have some horses or cavalry as part of her force.
That led to me converting the Kelpie (water horse) and Puca (shape shifter, often encountered as a horse) to keep the theme.
In this game I used the standard version of Epona from the rulebook - at just 180 points, she's not the most powerful goddess. The Celts version is altogether "beefier" with extra added powers (and increased point cost).