Gwen Stacy, better known as Spider-Woman, was patrolling one night, when a meteorite landed nearby and some black goo crawled out. She got possessed and her suit changed, now a darker version of the Ghost-Spider suit, with black instead of white. Her mood has also changed, the symbiote is influencing her darkest desires. Despite that, she is still a superhero. You are Peter Parker, her best friend, also know as Spider-Man. You don't know she's Spider-Woman, she doesn't know you're Spider-Man.