Do you have your partner's thyroid labs that you could post for us, along with the corresponding reference ranges, so we can see exactly what her thyroid hormone status is?
Duphaston is a synthetic progesterone that's used for a variety of conditions related to the menstrual cycle, endometriosis, etc. While Graves Disease can disturb menstrual function Duphaston is not the sole medication given to control Graves Disease.
Graves Disease is controlled with anti-thyroid medications, such as methimazole or PTU; these are medications given to stop the thyroid from producing thyroid hormones.