The Right Universe (гет)

After defeating Voldemort, Harry becomes consumed with creating a transition potion. Months of obsessive work destroy his relationship with Ginny, but he doesn't care, this is all that matters. When he finally drinks the potion, something goes catastrophically wrong.
She wakes in an alternate universe as a seventh-year Slytherin, her body finally right, her mother's face in the mirror. But the Dursleys are far worse to a girl, and Harry's only refuge is Severus Snape.