"Her acne's loads better lately - and she's really nice!"
-- Hermione Granger (GF22)
Eloise Midgen (or Midgeon) was a Hogwarts student in the early 1990s.
Eloise tried to curse off her acne and had to have her nose re-attached 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).
With the death-count rising in both the wizarding and Muggle world after the second rise of Voldemort, Eloise was one of the first students to be removed from Hogwarts School by their parents because of fears over student safety (HBP11).
Commentary
Etymology
Eloise comes from old French Héloïse, which is probably derived from the Germanic girl's name Helewidis (heil "hale, healthy" and wid "wide") (Behind the Name).
No information is available for either the Midgen or Midgeon surname.
Notes
Eloise never appears in the books in person, but is mentioned several times by other characters. She may be in Hufflepuff, since the Hufflepuffs chatted about her in a very familiar way in Herbology class (GF13).
Eloise's surname
Her surname appears as "Midgen" in all the Scholastic editions and e-books in the US. It was also spelled "Midgen" in the UK editions of Harry Potter and the Goblet of Fire (GF13, GF22). However, two later books in the UK, in both the first editions printed by Bloomsbury and the UK e-books, her surname is spelled "Midgeon" (OP17, HBP11).
So, the real question is: what is the primary spelling? Three-fifths of the UK occurrences and all the US occurrences use "Midgen", but the final UK occurrence is "Midgeon". It is unknown whether this was an intentional change that just never properly got back-added to the earlier book, or just an error in the UK and never corrected. Twice. --ibid/td
From the Web
Harry Potter Wiki: Eloise Midgen
WizardingWorld (Pottermore) features: Unsung Heroes: Poppy Pomfrey