She grew up hiding in apocalypses. Also, once pruned you go to the Void but it's never said how aging works there. Even though the TVA exists outside of time I don't see how people wouldn't age. You age as you are living but maybe the Void is different because Kid Loki was still a kid but we also don't know how long he's been there. I just thought of something, how did they live there? Where are they getting food and the ecto cooler drinks? Do drinks get pruned?