What Causes Delayed Periods Followed By Heavy And Prolonged Bleeding?

My mom is 43 yrs. old, she has a history of thyroid problem and is anemic.. Her period was late for 3 weeks and then she had very heavy bleeding.. She went to a gynecologist and she was told it was a thickened uterus due to hormonal imbalances. She's on a drug called 'duphaston' I think and also on iron supplements as her hemoglobin level dropped to 7.. She's not bleeding as heavily as she used to a couple of weeks ago but the bleeding hasn't stopped completely.. The gyne. told her that the bleeding is supposed to stop completely 3 days after starting the pills.. I would like to know what you think about this? and how longer would she be suffering..? Thank you