First of all, the way you've voiced these characters is nothing short of brilliant. They sound ever so much as they do in the books, which is quite an achievement, given the maturity and depth you've added to Myrtle.
Exploring how Minerva interacts with her contemporaries (as she was in school with both Myrtle and TMR) is a favorite of mine, and you do it very well here.
I love how you have Minerva teaching Myrtle about love and sex, and the matter-of-fact way Minerva regards her love life (and the travails thereof). Her grief is so strong--the grief of lost chances that parallels Myrtle's grief over missing the chance to love Olive in the flesh.
The way you address the issues of justice regarding spectral presences is deft and poignant. And Amelia's gentle education of Minerva is wonderful and unexpected--but totally believable. Too, it's rather sweet that Minerva continues to be ignorant of some of the sapphic love around her (Rolanda and Griselda in the Prefects' Bathroom indeed!).