She's a "mutate" given powers to by Magneto. I wouldn't mind if they just retcon that out and make the Savage Land Mutates into mutants, though. It doesn't make sense for Vertigo and Lorelei to always be with mutant groups when they aren't mutants themselves.
Also, the Marauders are just confusing. I think the original Vertigo is still in the Savage Land while the clones of her are still floating around here. But why she wasn't with the other clones in Hellions I have no idea.