What Causes Persistent Vaginal Bleeding Post Miscarriage?

MY GIRLFRIEND HAD A MISCARRIAGE ABOUT 4 TO 5 WEEKS AGO . AND WAS 16 WEEKS INTO HER PREGNANCEY. SHE HAS BEEN BLEEDING OFF AND ON FOR 4 TO 5 WEEKS KNOW. BUT TONIGHT SHE TOOK A SHOWER AND WHEN SHE GOT OUT SHE BEGAN TO BLEED PRITY HEAVLY LIKE A CONSTANT FLOW AS SHE SAT ON THE TOILET. IT HAPPENED ONCE BEFORE LAST WEEK. AND THEN AGAIN TONIGHT. ( SHE IS ANIMAC AND HAs not taken her meds lately. The hospital did give her a pill for her stomach to contract back.)