It's hard to say for sure. Sometimes a story might be based on real events but have fictional elements added in. Without more specific information, it's difficult to determine if it's completely true.
One could be a Supergirl fanfic about her teaming up with other superheroes from different universes to fight a powerful cosmic villain. It would involve epic battles and interesting character interactions.
It's hard to say. Sometimes books or stories draw inspiration from real events but are fictionalized. Maybe some research could clarify if 'Significant Other' has a real basis.
To write a story for your significant other, begin with a theme that represents your relationship. Build the characters based on your personalities. Make the story have a beginning, middle, and a touching end. Don't forget to sprinkle in some inside jokes or private references that only the two of you would understand.
One challenge could be the difference in energy levels. A younger person might be more active and want to engage in more strenuous activities, while the older partner may not be able to keep up. Another is health issues. The older partner may have more health problems that require extra care and attention.
If Barry kidnapped Supergirl in fanfiction, it could be a really interesting plot twist. Maybe Barry has been affected by some sort of red kryptonite - like substance that makes him act out of character. This would lead to a conflict between the Flash and Supergirl's friends and allies. They would be confused as to why Barry would do such a thing.