Firstly have you checked all the seams of the fabric to see if there is any details printed on it like the manufacturer, fabric name etc.?
My first impression is 70s or 80s home decorating fabric someone took a liking to and made a dress from. The dress style is a generic peasant dress style that featured from the 30s to 70s so showing close ups of how the dress is finished at the seams, finding out whether the thread is cotton or made made (via touch or burn test) and giving the bust/waist and length measurements will help to determine when it was made.