The other Barnes

Sergeant James Buchanan Barnes had a 15 year old little sister who was not only the only female in the howling commandos, Mia Barnes was the only female solider in the 1940's.
When Mia and Bucky are rescued by Steve from Zola's labs they are both different.
What if Bucky never fell of the train?
What if Mia did instead?
What if Bucky and Steve crashed the Hydra plane into the Arctic together?
When they wake the first thing they do is look for Mia, but are they 70 years to late?