As per the clinical case scenario your sister in law appears to have retained product of conception and is been currently been treated for the same by her gynecologist . If her follow up ultrasound
fails to visualise any remnant product of conception which is possible , as even a small portion of tissue left behind can cause bleeding and during this time her endometrial architecture would be distorted due to repeated bleeding and medications so i woulnot completely rely on her ultrasonography
report and try look at the clinical scenario. If she is still having bleeding per vagina then it is better to do a dilatation and curettage
. For more information ask her to consult with her gynecologist . Take care.