Evanescence, or as rendered once in this story, 'Evinezenze', is a Gothic band lead 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, Evanescence, or rather Amy Lee get mentioned a lot besides the story's name. In the very first chapter, for example, Ebony claims a lot of people tell her she looks like Amy Lee (and that if we don't know who she is, to get the hell out).
Some of her 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'). Also, she describes one outfit as looking like one Amy Lee wore to the Grammys once. Also, one chapter was named after another Fallen song, 'Bring Me To Life'.
Because of the supposed resemblance, many pictures of Ebony are edited ones of Amy Lee.