In some cases, it could be herself. Maybe she pushed herself too hard in her work or training, and her body or mind couldn't take it anymore. This self - inflicted harm could be a key part of the fanfiction's plot, as she then has to deal with the consequences and learn from her over - zealousness.
Most Oliver and Felicity fanfiction focuses on their relationship. It often explores their love, trust, and how they support each other through difficult times. For example, some stories might center around how they deal with Oliver's past traumas as a vigilante.
One possible fanfiction could be that Felicity discovers she's pregnant unexpectedly. Maybe she initially tries to keep it a secret from Oliver because she's worried about how it will affect their superhero lives. But eventually, she has to tell him and they have to figure out how to balance their duties and the new life coming.
It's also possible that Tommy hurts Felicity's reputation. In a social or political setting within the fanfiction world, Tommy could spread false information about Felicity. This could be due to his own insecurities or a desire to gain an upper hand in a situation. Felicity would then have to fight to clear her name and restore her standing in the community.
It could be about a character named Felicity being inserted into the Avengers universe. Maybe she has some unique powers or relationships with the Avengers in this fan - made story.
Perhaps in a fanfiction, Oliver and Felicity are transported back in time. They have to adapt to the old - fashioned ways of that era while still maintaining their modern - day love for each other. They might face some difficulties, but also find new ways to express their love and support.
Ra's al Ghul might be another possibility. He has a long - term view of things and Felicity's intelligence could be useful for his grand plans. He might want to use her to build some sort of advanced weapon or decrypt important information.
We don't really know who Felicity is without reading the story. She could be a young girl, perhaps a main character who the Christmas surprise is centered around.
A fanfic could also explore the reactions of the other characters like Diggle and Thea. Diggle might offer his fatherly advice since he has experience with fatherhood. Thea could be excited about becoming an aunt and start planning all kinds of things for the baby. This would add a touch of family - like warmth to the often - intense Arrow universe.