The Magenta Spy

DISCONTINUED

When Bucky and Rebecca's parents died, the were separated. Rebecca was sent to a boarding school and Bucky was sent to their parents' friend. But after Bucky was taken by Hydra, they soon discovered that he had a little sister, her boarding school was attacked and she was taken and put under ice. 80 years later, Rebecca is placed in the red room and known as The Magenta Spy

Drokov sent Rebecca on a mission kill a former HYDRA Assassin. She had no inkling that her brother would be her enemy...

This takes place after endgame and for plot reasons this will happen as if, hypothetically speaking, Black Widow the movie didn't happen.

Disclaimer: I don't own these characters nor do I own this world. It's the MCU