Her Resurrection

Sadie Gaunt, a young witch from the prestigious pureblood family of Gaunt, defies her family's expectations by rejecting an arranged marriage. After graduating from Hogwarts, Sadie faces pressure from her family to marry Alphard Black, a fellow pureblood from a powerful family. However she runs away to her squib uncle Charles Xavier a mutant living in America

Book 1 of a witch amongst mutants

I do not own Harry Potter or The X-men!!!! The timeline is a little different Also there's no snakeface Voldemort in this story.