The most common causes of this are:Significant weight gain or loss ,Over-exercise,Poor nutrition (or a diet too high in carbohydrates),Smoking,Excessive alcohol use,Eating disorders,Increased stress,Polycystic ovarian syndrome/estrogen dominance,Uterine abnormalities (fibroids/cysts/polyps/endometriosis).
She need following a complete physical, including evaluations of thyroid function. Also, a complete blood count (CBC) test is quite important for the diagnosis of anemia. A pelvic exam is critical to rule out any uterine abnormality, a cervical polyp or fibroid, or a uterine infection.An ultrasound will be required to evaluate the uterus, the ovaries and the fallopian tubes.
The underlying cause is first to be detected & then the treatment should be done accordinglly.I advice you to consult the experienced gynecologist of some higher medical institute
Hope this helped.