Thanks folk, you've been very helpful. (I started typing this before I saw the two notes from Lisa, which further confirmed that this is "my" Christina.
Yes, the parent details Lisa has given are correct. And, thank you to RJ137, she did have an elder brother John Duncan Simpson, although I didn't know he had emigrated (I hadn't done any research on him as Christina was only in my family tree by informal adoption after both her parents had died when she was an infant.)
And her grandmother was Mrs Janet Simpson, who lived until 1923. It's quite likely that Christina would have given her grandmother's name, since not only had her natural parents died when she was an infant, but her adoptive parents had both died when she was a teenager!
So this really does look as if it's her. There doesn't seem to be any other Christina Simpson from Aberdeen and of the right age who ticks these boxes.
And thanks for the links to the 1930 and 1940 censuses - the immigration date of 1920 ties in, so it does look as though she continued her rather sad life as a servant, in Seattle then San Francisco.
Re the trip to the UK in June 1931, the same Christina Simpson (54 Esslemont Avenue, Aberdeen) went back on the Britannic from Liverpool on 10 October to Boston / New York.
http://search.ancestry.co.uk/cgi-bin/sse.dll?_phsrc=JNl35&_phstart=successSource&usePUBJs=true&gss=angs-c&new=1&rank=1&msT=1&gsfn=christina&gsfn_x=0&gsln=simpson&gsln_x=0&msbdy=1893&msbdy_x=1&msbdp=5&cpxt=1&cp=11&MSAV=1&MSV=0&uidh=mj2&pcat=40&h=142344488&recoff=6%207&dbid=2997&indiv=1&ml_rpos=3 And the clincher as far as I am concerned is that her 1972 death record on the US Social Security record has her date of birth as 22 Oct 1893, the same as "my" Christina.
https://familysearch.org/ark:/61903/1:1:J5XX-5Y6?print=trueI'll leave this thread open for a few days, just in case anyone else comes up with some more information about Christina, and if not then I'll mark it as COMPLETED. Many thanks to all of you for helping me fill in this blank in my family history. I'm just sorry for Christina that she doesn't seem to have had all that great a life.
PS to Lisa in California - yes, if you have any more info about Christina that you are willing to release by private message, that would be very kind of you.
PPS to RJ137 - thank you for the death certificate and obit notices, sent almost simultaneously with my own post. Very informative.
