She is referred to as "the youngest girl to appear so far" (in the anime), though it is unknown how old she truly is. She seems to have a connection with Nunotaba Shinobu.
SpoilerIt is later revealed that Febri is an artificial human created by a group of scientists, Shinobu Nunotaba being the one who programmed her using Testament, much like she did with the Sisters project.
However her body is unstable and the only way she can survive is by eating the odd flavored lolipops she carries in her purse which destroy the poison released by her altered body cells, without them she will eventually fall into a feverish state and, if left untreated, it will kill her.
CV: Nomizu Iori