Waiting till Zawaal While in Haidh to Fast in Ramadhaan

Q: You stated that a sister should commence with fasting before fajr time has entered. If I did not misunderstand is that the case with nafl? I wanted to clarify if there is any difference in Ramadan. We read in Turkish kitabs that in Ramadan we should wait until zawaal with fasting and if we are sure that we are clean before zawaal and haidh has ended, then ghusl should be taken and make niyyat and fast. Please correct me if I understood wrong because I was practicing on that.