Fiore Loderia Lavigneri

フィオーレ・ローデリア・ラビニエリ, Fio

A member of the runaway spirit squad and secretly a member of Vintage who obsess with bringing back the age of 'Old Hell'. She first appeared observing Keima and Elsee extracting the escaped spirit from Yui.

Later she disguised herself as Kusunoki and caused the spirit inside to Hinoki to increase exponentially. Using a modified spirit sensor she confirmed the presence of Apollo inside Kanon and ambushed her stabbing her with an enchanted blade.

Source: Wikipedia

She looks like she is a low level member of Vintage, by her reaction while stabbing Apolo... (Source: Chapter 116) As also she seems to be the same school generation as Haqua and Elsie (Source: Chapter 101)