I just came across something - and while I admit I haven't read all the threads, I did do a keyword search and nothing about this came up... so here goes:
I did a search on Ancestry using the 7101 El Caballo (Boise) address as a keyword.
There was a Barker family at that address and one of them was named Becky. The birthdate of this Becky was in 1952. I am seeing records for this Barker family at this address in 1987 as well as 1993 which means they were there at the time that she sent that application.
There was a Donna with a 1961 birth year - shows a different address but same phone number as the 7101 El Caballo Barkers.
There are a few other Barkers there but I don't want to post their names here since it's unlikely that any of the others could be her due to their ages/genders. But if anyone wants to see if they're all accounted for, I can let you know how to find them if you have Ancestry.
Edited to add:
Here is an obituary of one of them. Notice it says she often had visitors stay for a couple nights, I wonder if that was the case with this girl. It seems the three female Barkers from Ancestry are accounted for in the obituary but there is also one who apparently predeceased her (I did not see her in my Ancestry search).
http://www.legacy.com/obituaries/idahostatesman/obituary.aspx?pid=166530374