Upside Down • Legends of Tomorrow WTM

Jade Allen was a journalist. But when the particle accelerator exploded, she was given the power to control the elements. She was always the spare hero for Central City, second to her younger brother Barry or "The Flash". That is, of course, until Rip Hunter recruits her and eight others to join him on a mission to save the world from Vandal Savage. During this time, she meets people she calls family

Or...

In which cannon Arrowverse watches an alternate universe where Barry has an older sister.

Disclaimer:
I only own Jade and any storyline I create. The rest of the credit goes to the owner of "The Flash", "Arrow", and "DC's Legends of Tomorrow"