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.
One inspiring Supergirl story is her fight against powerful villains to protect Metropolis. She uses her super strength, flight, and heat vision to keep the city safe. For example, when a group of alien invaders threatened the city, Supergirl was the first to stand up and fight them off, showing great courage.
Supergirl's origin typically starts with her being from the doomed planet Krypton. She arrives on Earth and gradually discovers and masters her powers while facing various challenges and adventures.
Supergirl has super strength which allows her to lift extremely heavy objects. She also has heat vision that can be used as a weapon. And of course, she can fly. Wonder Woman, on the other hand, has super strength as well, but she has unique weapons like the Lasso of Truth which can force people to tell the truth, and her indestructible bracelets which can deflect bullets.