Fem Harry Potter X avengers
Harry is a female and is the master of death and becomes immortal after the battle of Hogwarts.
She spends decades searching of a way to get rid of her immorality but after she finds what she thinks is a very extremely powerful spell that should remove her imortailly but it sends her to the marvel universe.
Where she meets everyone as kids helping them.
And years later after she is caught on camera saving someone shield send the avengers after what they think is a Mutant or enhanced as female harry does spells without her wand and they don't have to be verbal after decades of using magic.
When she gets surprised and then gets drugged. The avengers are All surprised to remember her from their childhood memories as the woman that helped or saved them