You decided to play as the woman, because you felt like this was during a time when women weren't strong enough to fight, besides seeing a blonde woman during the 50s seemed attractive to war veterans. With a new war happening, and Power Armor, you'll be able to destroy anything in your path with a ton of strength.
Once you've selected your character, you felt your entire body changing, as you took a look at yourself. You felt your whole skin become the same color as your nails got longer, and your clothing fused to become dress you saw the blonde woman wear, as you developed her hair, her breasts, and her hourglass. You took a good look at yourself, and found that you have officially become a full grown adult blonde woman from the 50s, like the one in the video game you were playing.