A third plot twist could be that the attack is a diversion. While Clary is fighting the demon, something much more significant is happening elsewhere. Maybe a powerful artifact is being stolen or a key location is being infiltrated, and by the time she realizes it, she has to race against time to stop the real danger.
Well, she might be rescued by her friends. In many fanfictions, her Shadowhunter comrades would come to her aid, using their unique skills to fend off the attackers.
Alec might also come to her rescue. As a skilled Shadowhunter, he has a strong sense of duty. Plus, he's part of Clary's group, and he wouldn't stand by and let a fellow Shadowhunter be attacked by a demon.
Another character who has a personal vendetta against Clary or her family. For example, a jealous rival or someone who blames her family for past misfortunes. This would add a layer of drama and personal conflict to the fanfiction.
One possible plot twist could be that Sebastian's true motives for getting Clary pregnant are revealed to be part of a larger, darker scheme. Maybe he plans to use the baby for some sort of power - play within the Shadowhunter world.
One possible plot could be that Nicole is attacked while on a solo mission to gather information for the resistance. She manages to fight back briefly but is overpowered. Then Waverly races to her rescue, using her own skills and the power of their love to overcome the attackers.
Another option is a group of demons who have a vendetta against Clary or the shadowhunters in general. They might use torture as a way to break her spirit and gain information about the shadowhunters' defenses.
One possible plot could be that Clary gets drunk and ends up confessing her hidden feelings to someone she has a crush on.
It could be a group of out - of - town bounty hunters. They might have heard about Nicole's reputation as a tough cop and see her as a valuable target to bring in for some kind of reward. Maybe they are working for a shadowy figure who wants Nicole out of the way so they can take over the town's law enforcement.
One possible plot twist could be that the kidnapper is actually an ally in disguise, trying to protect Mario from a greater threat. For example, they might be taking him away from Bowser's clutches in a way that seems like a kidnapping but is really a rescue mission.
Another plot twist could be that the pregnancy progresses at an extremely abnormal rate. This could put Renesmee's life in danger and force her and her loved ones to find a way to slow it down or deal with the consequences of a very rapid development. It could also lead to some unexpected revelations about her own nature and abilities.