Should missed prayers be made up, or is repentance sufficient for not praying, in the case of a virgin girl experiencing intermittent brownish discharge resembling menstrual blood, accompanied by symptoms of menstruation?

Yellowish and brownish discharges are considered menstruation if they occur during the habitual period, in which case you are prohibited from prayer and fasting, and you must perform ghusl (ritual bath) after their cessation. However, if they occur outside the habitual period, they are considered istihada (non-menstrual bleeding) and do not prohibit prayer or fasting. Instead, you must clean yourself (istinja') and perform ablution (wudu') for each prayer after its time has begun. If you have missed prayers when they were obligatory to perform, it is more cautious to make them up (qada').