While most girls tend to talk about this with their mothers, there is no reason why Dad has to be totally excluded from this educational process. It would probably be helpful for you to read a bit about puberty so that you'll understand the stages of development that she is going through, and be able to discuss it if she has questions. It would also be a good idea to identify some female adult that your daughter knows well and is comfortable with, to specifically talk with her about puberty and menstruation. Additionally, the time to do this is now. It is very helpful if a girl knows what is happening to her body before the changes actually start. A lot of fear, anxiety, and misunderstanding can be prevented in this way.
Advice for Dad About Pubescent Daughter
Pediatrics Expert Advice from Shari Nethersole, M.D.