"Her acne's loads better lately - and she's really nice!"
-- Hermione Granger (GF22)
Eloise Midgen was a Hogwarts student in the early 1990s.
Eloise tried to curse off her acne and had to have her nose reattached by Madam Pomfrey (GF13), but it ended up off centre (GF22). Ron irritated Hermione by saying he wouldn't want to go to the Yule Ball with Eloise because of this (GF22). To this day, Harry, Ron, and Hermione speak of her as the standard against which really bad acne must be measured (for example, Hermione compares her acne to the pimple curse on the list of D.A. members (OP17)). Eloise was one of the first students to be removed from Hogwarts by their parents (HBP11).
Other canon notes and references
Eloise never appears in the books in person, but is mentioned several times by other characters.
Eloise may be in Hufflepuff, since the Hufflepuffs chatted about her in a very familiar way in Herbology class (GF13).