Update to story as of July 16, 2019: According to the Facebook page of the Rosebud Sioux Tribe Law Enforcement Services:

It is with our condolences, the Rosebud Police reports that the search for Waniyetu Loves War AKA Autumn Emery has been concluded. We would ask you to say prayer for her family and friends. We thank everyone for the tips that we have received and to everyone who participated in today’s search.

The post did not indicate the circumstances as to why the search was concluded. 

Waniyetu Loves War, also known as Autumn Emery, was last seen on July 7, according to a missing person poster shared by community members.
She is 19 years old and was last seen by Old Two Strike wearing a green shirt and a brown skirt. She is 5 foot 3, weighs 120 pounds and has long dark brown hair.
Anyone with information is asked to contact the Rosebud Police Department Dispatch at 605-856-2365, the RST Admin Line at 747-5928