A very confusing ruling about menses…..

Respected Mufti, I would greatly appreciate it if you would tell me the ruling about the following situation: a woman has a normal menstrual cycle of 7 days each month. She usually starts on the 24th of every month. However what happens is that in September she starts on the 24th but she doesn?t stop after 7 days and her bleeding continues for approx two and a half months. What I mean is that the bleeding continues from the 24th of September to the 13th of December. For 7 days she sees absolutely nothing (from the 14th to the 20th). Bleeding resumes on the 21st and ceases after 7 days, similar to her previous habit. After this her period returns in January on the 21st for 7 days as usual. So, firstly, what should she do in the first instance when her bleeding exceeded 10 days and continued? And secondly, are the 7 days of bleeding after the break counted as her period or Istihaadha? Generally, what should this woman do?