They meet on their first report for duty. It's nothing, really, they're just standing beside each other when they line up. Diane sticks out a hand and Peggy shakes it and when Diane smiles at her, she feels something brighten inside her. They're fast friends, but the girls around them all whisper that it's something more, and maybe it is.
For a while they're stationed together. Diane's repairing damaged planes on-site while Peggy is being trained. They spend breaks together, and nights in each other's beds, whispering and giggling.
Peggy is recruited to the American army, but she doesn't leave the base because, well, sooner or later the boys would be coming over here. Only weeks later and Diane has been asked to ferry planes about Europe. They have a hissed row in the night, and Peggy begs her not to go. She's seen pilots come back bloodied and broken, or dead.
The next morning Peggy wakes early, before the bell, and Diane is nowhere. Unthinking, she runs to the radio tower. The metal grates cut her bare feet. From the window she can see a plane coasting out onto the field. She radios in to it.
"Diane. Don't go! Please stay here with me."
There is radio silence for a long time. Then static. Then, "I have to, Peggy. I love you."
Four months later, Peggy meets Steve Rogers in a line of soldiers.