Oh my gawd...

 I was worried about my daughter when she was 16 and didn't have her period yet.  She finally admitted that she had it since she was 13 but denied it when I asked her about it for 3 years.
My middle daughter I can't really remember but I think it was around 13, too.  My youngest started when she was 9, too.  Way too early but she started puberty early.  By the time she was 7 she had already started growing hair.