The best answer is
The author uses indirect characterization to describe how Millicent feels.
While the author's description of the ceremony gives the idea that Millicent probably looks pretty gross, with egg on her head and whatnot, the passage mainly gives the reader an empathetic view into Millicent's experience.
The scene is described as sounds and sensations from Millicent's point of view. She feels her stiff hair, and the cold egg on her back, hears the stifled laughter and crunch of the egg breaking. We can imagine the intensity of the experience, blindfolded and hearing, feeling, and probably smelling the unpleasant experiences during this initiation.
In the end, the passage concludes with: "It was all part of the ceremony." This final sentence may relay how Millicent is processing the unpleasant initiation, rationalizing that this is just a step on her way to being part of the group.
