My daughter has not started her period yet. Why?

Hi doctor,

My daughter is 14 years old. She is 5'2" height and her weight is usually between 110 and 115 pounds. She has not started her period yet and I am a little bit worried. She started puberty growth when she was 11, so it is almost three and a half years now. She has all the symptoms of premenstruation now as well. It includes frequent discharge, mood swings, occasional cramps, pubic hair growth, growth of breasts, etc. I did not get my first periods until 16 years of age, but she is much more developed than me. Also, the last time when we went to the doctor, they told us to expect it to come within the next few months, but it has been almost a year now. I am worried that something is wrong and that is why she has not got it. I know that this is a common concern among teen girls, but I would really appreciate your advice. Thank you very much.