I think your last comment is correct: "...perhaps Jeduthan (II) felt that he wasn't obligated to stay in Massachusetts once his mother had died."And I do believe that the family stories were true concerning somebody...but the subject's name was confused.Finally, as mentioned in my previous post, there is this record:
Death Record, "Mrs. Torrance; female; death date: 27 Feb 1854; death place: Enfield, MA; age: 74; birth date: 1780," Source film no. 960170; FamilySearch.org, www.familysearch.org.
"Mrs. Torrance" was in the right town, had the right name, and was the correct age (based upon her stated age  in the 1850 U.S. census).Who else with the Torrance name could possibly fit this description?I don't believe it was coincidental that her son Jeduthan II and Emma left their home in 1854, especially if his mother had died early that year, and his siblings had gone west.Given this death record, the critical fact that she cannot be found in any Oregon records (although her children can be), and her son's departure from Enfield in 1854, she is almost certainly Eunice (Gibbs) Torrance, widow of Jeduthan Torrance of Enfield.I have to mentally stack that against family stories of a woman, aged 74+ years, wandering hundreds and hundreds of miles across an unforgiving landscape.Though it would be wonderful to have ship passenger records, I don't believe they are necessary.The preponderance of evidence supports her death in Enfield on February 27, 1854.