What is the ruling on the fasting and prayer of a woman who saw light red blood after seeing white discharge on the sixth day of her menstrual period, which lasts seven days, and must she make up the days she did not pray or fast?

As long as you find blood during the menstrual period, it is not permissible for you to fast or pray. If the blood stops, or you see the white discharge, then this is a sign of purity, and ghusl (ritual bath), prayer, and fasting become obligatory. There is no significance to the fluctuation in the duration of the menses, as it can increase or decrease. You were correct in abandoning prayer before the end of menstruation, but fasting for a menstruating woman is not permissible, and she must break her fast. If menstruation ceases before Fajr (dawn), fasting becomes obligatory, even if she does not perform ghusl until after Fajr, because ritual purity is not a condition for the validity of fasting. You are not required to make up the prayers missed during menstruation, but you must make up the missed fasts. Upon seeing the sign of purity, either by the white discharge or dryness, you must perform ghusl.