Period timing

Ruthie • 21 years old looks Younger than am. Boyfriend military. Don`t plan on having kids. Not educated WELL on birth control but is on the pill
So my lil sister jus started her period two month ago and sence she is the to redo our schedule its gone so out of wack evryone in the house has had two periods last month.its ty here a way without pills to regulate her period?