The Shoshone Oral Tradition is that Sacagawea lived a long life and died an old lady.  They say that following the Lewis and Clark Expedition, she argued with Charbonneau and left him.  Then she went to live with the Camanches for a little while. When she went back with the Shoshones she was reunited with her son Babtiste, and with the nephew she adopted.
 

Sacagawea
Alana J. White
1997