Disclaimer: I am going to be talking about bullshit from a fandom I participated in when I was 11-14. I understand some of you may have reservations about bronies, but please cut me some slack. I was still a little kid at the time.
ElieMonty was extremely well-known in the brony fandom for various reasons, but the primary reason she was so well known was her covers and her voice work. She was well-known among fans as THE "official" fan voice for Rarity (the haughty ojou-samaish character) and Octavia (a background character cellist). I will spare you the suffering of embedding the video directly, but a
popular fan animation of said background character features her singing, and that always left a pretty large impression on me when I was young because of her skill.
Another rather important role she played was as the... rather unnecessarily "hot mom" character in another popular fan animation,
Button Mash Adventures. Again, although we don't see her singing this time, her voice range is pretty well represented here. Of the two animations I'd suggest watching this one to get an idea of her over the other.
This reputation she gained made her one of the premiere characters in the fandom, alongside other famous girls such as Nowacking (voice of a few characters in Hellsing Abridged, played the "DJ" background character opposite Octavia, eventually went ftm) and Jenny Nicholson (known for youtube video essays now, but well known when she was younger for basically single handedly making the definitive MLP abridged series, Friendship is Witchcraft). Elie was a guest of honor at various brony conventions and enjoyed a pretty large fanbase of spergs.
As time went on, and the brony fandom entered its twilight years, many of its fan content creators would move on to different ventures. Some of them went into general fandom stuff (you probably know TheLivingTombstone moreso for his Five Nights at Freddy's song than anything he made as a brony) or other random internet stuff, and some of them went into the anime fandom/voice acting community. Clearly, in the case of Elie here, she went for the latter, and honestly that's probably for the best.
By now, she's probably pushing 40. She was pretty clearly in her 20s when she started as a content creator back then. In other words: Hag lovers, you won.