Board Thread:Online Discussion/@comment-10104661-20141207192710/@comment-86.130.80.150-20150128220601

Nightmare Moon is voiced by Tabitha St. Germain (also Luna Rarity and oddly Haro from the Gundam dub) Estre doesn't seem to be listed (list here) she must be under just "Additional Voices" so its hard to tell who voices her, she could be Tara Strong (Twilight Sparkle and Raven from Teen Titans).