XD Lily's kind of an interesting mix of inexperienced/naive sweetheart and battle hardened genetically engineered weapon. She also appreciates people who don't try to tell her she shouldn't fight and that she should just be a normal kid. She appreciates that it's a kind wish for her, but she also doesn't get why they'd be so opposed to her fighting when she can survive things others don't.

Considering that Walter's just a couple of years older than her, IDK if he's encountered the "you're too young to fight" attitude from people but it's something they can bond over.