She did not know the signs of puberty so she did not fast in Ramadaan, out of ignorance
Question

According to custom in some Muslim countries, menstruation is regarded as the sign of puberty for women and no attention is paid to the other signs, such as the growth of pubic hair etc, which are known from the books of fiqh. 
As a result of this kind of custom, one of the sisters started to observe the obligatory fast of Ramadaan after she saw menstrual blood, although at that time she was thirteen years old and she already had pubic hair before she got her period, but she does not remember whether that hair was coarse or not, and she does not remember how many years she did not fast after that hair appeared.  My question is: 
1 – What are the signs of a woman’s puberty, according to sharee’ah or to custom? 
2 – What is the ruling on this sister’s not fasting during those Ramadaans when her hair had started to grow but she had not yet started her periods, if the custom on this issue is contrary to sharee’ah?.
Praise be to Allah.A woman is deemed to have reached puberty when one of four things happens: 
1 – When she reaches the age of fifteen.
2 – When her pubic hair grows, which is hair around the private parts.
3 – When she emits maniy (fluid released at climax).
4 – When she starts to menstruate. 
If one of these four things happens, then she has reached the age of puberty and she is now regarded as accountable, and she is obliged to do acts of worship just like adults. If a woman did not know that puberty begins in this manner, then there is no sin on her for not fasting, because she was unaware, and there is no sin on the person who is unaware so long as he was not negligent about learning or finding out when he was able to do so. But she must hasten to make up the fasts that she missed because when a woman reaches the age of puberty, she becomes accountable and she must make up the fasts that she missed during the time when she was accountable. She must strive to work out how many days she missed after she reached puberty, and hasten to make them up so there will no longer be any sin on her.