Hey thanks, Phyllis. Yeah, after my last post I was able to locate the 1920 and 1930 census for Adele/Adelheid, and she still had the same surname, so I was coming to that same conclusion about a remarriage as well.
Thanks for pointing out the 1900 census entry. I'd been having a devil of a time trying to find it. Just did. Ancestry had it indexed under "Angus" Sanger - I read the given name as "August", but this all still fits well with what I already know.
I'm interested in these folk because I've been researching all of my Zaenger kin who came out of Wangen, Alsace and the surrounding area. I had Gustave and three siblings and their parents in the Wangen civil records up until the early 1870's, then they all seemed to disappear, except for the youngest daughter.
I still would like to find out what happened to Adele. I agree; I don't think the Napper connection is going to pan out either with my Adele, based on some of the index stuff I've looked over so far.