Have you heard a Serama crow yet? That's really stretching the terminology. It's hard for me too imagine your neighbor being able to hear them, much less figure out what she's hearing.
all roos, I have much older mfs right now and the pullets have combs MUCH smaller than that and not at all red. The combs are still yellow and they are about 8 1/2 weeks old now.
I feel bad that you didn't get the pullets you wanted.
This guide helped me determine the gender of my six. Hope it helps you.
According to UC Davis Veterinary Care Program.
2. Physical Characteristics (4-6 weeks of age)
a. Comb The cockerels comb is medium size and pinkish, the pullets is small and yellowish.
b. Legs The cockerels legs are sturdy and long, the pullets are finer and shorter.
c. Tail The cockerels tail is stumpy and curved, the pullets is longer and straight.
d. Back The cockerel has a thin line of stub feathers down the center of his back, the pullet has more advanced feathering along the center of her back.
e. Side of neck, flank and crop The feathering in the cockerel in these areas is poorly advanced, the pullets feathering in these areas is well advanced.
f. Wing bows In the cockerel the wing bows are bare, in pullets the wing bows are covered with small feathers.