Like I said, the posture. now what's Ozy's excuse? he also looks a litte older.I think it's the way she's sitting that makes Millie look older, with her legs crossed like she's wearing a skirt. Also, she's making sure to cover her chest with her towel, something a kid wouldn't really care about with friends and family.
Heck, even though I'm kinda new to the strip *waves hi!* it seems she's somewhat known for her streak of errant nudism - the fact that she's wearing a towel at all is kinda odd, especially given how humid it must be in there.
P.S., Airport, or you get burnt and shaved.