No, Georgie didn't have the foggiest idea what was going on yet, so when she said that Gene looked more like a kid than usual, she meant that instead of the brother she knew who was learning how to grow a beard and starting to look like a man, before her stood a kid with a weight on his shoulders. The differences were minute, but for someone who grew up with someone who looked exactly like her, she was used to seeing the minute details most people missed.
"I dunno, why do you look 12?" she countered, exaggerating quite a bit, but then, that was what they did.