Aside from the "big sister" part (the Soldier isn't even sure what that kind of relationship would entail, to be honest; they have no memory of siblings), that sounds eerily familiar. Enough to make them stare in her general direction suspiciously. Still no eye contact, but it's clear they're looking at her.

And ten they do admit, "Mine, too. First friend in a long time. First person to make me realize I could have those." Not that they're very good at it-- neither the Soldier nor Scarlett.