My daughter has been unable to get in without us, ever. She is currently 19 (she looks younger), but has access thru AX Plat and passes (her own). I personally think it's a shame; there are many times when she arrives at EWR a few hours before Mr Fish, and I would feel better about her waiting in the PC rather than just sitting in the terminal. I never thought about her being walked in with someone. Maybe she could offer someone entry as her guest in exchange for being accompanied by an over 21. I doubt she would ever feel comfortable asking anyone though.
Robin