Nothing much is known about her, but it is assumed that she is a goth like Tara and Raven. She became a story-insert in Raven's story I'm Not Okay as the character 'Shadow', who became friends with Raven's Mary Sue character. She was later mentioned in the AN of Chapter Twenty Eight when Tara thanked 'fily 4 da help', assuming this is the same Filly mentioned in Raven's story. It is also assumed that Filly helped Tara with this chapter.
Another friend mentioned in the AN was Kiwi, though literally nothing is known about her either, other than the fact that she is also possibly in Tara and Raven's friend group.