Evanescence, or as rendered once in this story, 'Evinezenze' and 'Evonezcence', is a gothic band led by Amy Lee. 'My Immortal' is one of their most well-known songs, from the 2003 album Fallen. In 2006, however, Tara Gilesbie wrote the infamous Harry Potter fanfic of the same name, and thus the song is forever associated with the story, albeit very loosely.
While Ebony tends to spend most of the story rambling about MCR and GC, Evanescence and Amy Lee are mentioned occasionally as well, in ways besides the story's name. In the very first chapter, for example, Ebony claims a lot of people tell her she resembles Amy Lee (and that if we don't know who she is, to get the hell out).
Some of Ebony's wardrobe seems to take inspiration from Amy Lee's outfits, as at one point she wears her hair in the same style Amy did in the video for Going Under (or in this fic, 'Gong Under'). She also describes one outfit as looking like one Amy Lee wore to the Grammys once. One chapter was named after another Fallen song, 'Bring Me To Life'.
Because of the supposed resemblance, many pictures of Ebony are edited variants of Amy Lee photographs.