Watching this thread with interest!
She looks younger than 5 months to me. Her adult feathers haven't all come through yet and she looks quite straggly which you'd expect from an immature adolescent chicken. Her comb isn't red enough to be laying. If her breed are slow to mature that might explain why.
I see male hackles but that might be because they are still growing in. The saddles look round ended to me, not male and pointy.
The wing pattern colouring, well who knows. The final body colour isn't there yet, so it may change still.
I believe she _could_ be a pullet. Time will tell. The other chicken could have laid the egg. How does it compare in colour to the other eggs she lays?