I'm fascinated by "Necrosha" since Selene needs her due as an X-villain. After all, she's thousands of years old. I'm surprised they never used her as a villain in "Guardians of the Galaxy." (Even Ra's Al Ghul has fought the Legion of Superheroes.)
As we've seen on this board, Wolverine stabbed Rachel Summers to stop her from killing Selene. Hopefully, if Logan and Selene confront each other, that will be mentioned.
Selene could be placed into Captain America's origin. Selene is annoyed by the Nazis wanting to take over the world, and assists in the creation of a super-solider. From Selene's POV, after the Axis Powers are defeated, a squad of super-soldiers would be a smorgasbord for her. But only one super-soldier is created, and the rest is history.