Etta? No one knows. She left, presumably on a steamer to San Francisco, and disappeared into history.
As for Butch and Sundance, recent excavations in Bolivia did find 2 bodies, but neither belonged to B&S. Some azzhole on FB claimed that didn't prove anything, as lots of people were buried in that cemetery and they didn't dig everyone up. He then said that the excavations didn't prove that they weren't buried there. Never did get the point I made that you cannot prove a negative. Ah, the idjiots on teh intertubes! It's clear that 2 Anglo bandidos are buried in that cemetery, just not B&S, whose ID was done by Pinkertons from "eye witnesses" well after the 2 were dead and buried.
I for one land on the side of them surviving if only because of the sister's testimony - on film - that Butch came to visit her and the artifacts that she had that can be traced to photographs of Butch wearing some of them. Not definitive to be sure, but compelling at the least.