Go to the doctors if you are concerned but same thing happened to me. The brown discharge is normal if it's not a huge amount for a long periods of days. If not then that's fine. Keep and eye on it and track your periods and what's going on because that will really help if you are concerned. Some cycle are longer the others so don't be afraid if you think you are late on a period. Tracking will help you understand them more.
You should definitely check with your doctor if you are concerned. Try not to stress or worry to much that can cause your period to be delayed. All women experience different cycles. So again don't stress this might be your normal cycle. Just check with ur Doctor. Tell ur mom to make an appointment.