I just messaged you but for the sake of discussion...

Time. Must be after the war. Can't think of anyone other than Jayne interested in interstellar travel during a "devastating" war. Inara has to be old enough to be on track for House Priestess position. I'm thinking 3-4 years since Nandi banged up that dulcimer and headed out.

I think the other girls/boys were all Rim folk. Maybe from nearby planets shipped in to fill vacancies. But! Nandi may have befriended one or a few during her travels.