A pile of stuff that really doesn't help:
1904, both Frederick and Laura come from England on different ships. She is using the Mornement surname, and states she has never been in the USA before.
1910 USA census shows Frederick and Laura as married 6 years.
If they were married in the San Francisco area, a huge amount of records were destroyed in the massive earthquake of 1906.
https://www.familysearch.org/en/wiki/San_Francisco_County,_California_Genealogy1916
Laura gets on the ship, Missanabie, in Montreal, sailing to Liverpool, to remain in England permanently, giving the address she is headed to as 46 Loncroft Rd, Camberwell. The ship is shown as arriving 04 Sep 1916.
Elsie's naturalization showing marriage date 12 Oct 1916
https://www.familysearch.org/ark:/61903/3:1:33SQ-GBVN-KJL?i=498&cc=1849982 1919 Nov
Laura returns, sailing from Antwerp to Quebec, headed for San Fran and husband F.M. Mornement.
I think this is where the massive confusion seeps in. It appears that she left him back in 1916, but returned and found him married.
However, I think it is highly possible that they were never married, because I think, (but cant prove or disprove), that she was already married to a William Arthur Jones, in 1902, in Southwark, so Fred was free to marry. Shows Elsie as a Mornement Nov 1920
https://www.newspapers.com/article/san-francisco-bulletin-margaret-cowperth/134874784/1926 - 1928
Multiple mentions of court dates for Kellet v Mornement, with the last being F.M. Mornement applying for discharge, bkt. (I originally thought bkt meant bankrupt, and maybe it does? No idea of what it was all about; I can't find anymore about it. Something to do with business at any rate!)
Olga is artist and decorator 1932
https://www.newspapers.com/article/the-press-democrat-olga-artist-decorator/134876496/1934 Mornements/Wrights visit
https://www.newspapers.com/article/santa-rosa-republican-wrightmornement/134874486/1935 visit
https://www.newspapers.com/article/the-press-democrat-mornementwright/134874547/1935 another visit
https://www.newspapers.com/article/the-press-democrat-mornement-visit-wrigh/134874621/(There are dozens of such visits between the Wrights and the Mornements, but no point in posting them all, just trying to give you the jist of it all)
marriage license notification Nov 1940 . Note this is for an actual license, not the previous "intention of marriage".
https://www.newspapers.com/article/salinas-morning-post-license-to-wed-morn/134875148/Olga's son marriage Apr 1942
https://www.newspapers.com/article/the-press-democrat-marriage-of-moncheur/134875213/Olga's sons 1945
https://www.newspapers.com/article/the-press-democrat-olgas-sons/134876613/tragedy 1952
https://www.newspapers.com/article/the-press-democrat-olgas-grandson/134875582/Girault Wright obit no mention of Olga 1956
https://www.newspapers.com/article/the-press-democrat-obituary-for-girault/134876715/Fred's obit Apr 1974
https://www.newspapers.com/article/the-san-francisco-examiner-f-m-mornement/134874998/olga obit 1981
https://www.newspapers.com/article/the-press-democrat-obituary-for-olga-wri/134875267/1990
Cannot find obit for the daughter, Fredericka J Carman, but The San Franscisco Examiner, 15 Jul 1990, has a list of cremations scattered at sea, by the Neptune Society, and there is a Fredericka J Carman on that list.
To find divorces pre-1962 in California, you have to know exactly which courthouse dealt with it. As there was a license to marry Olga, I would think Fred and Elsie would have had to have divorced legally.
I will keep hunting for a bit, but I do think the actual documentation you need may remain your dreaded brick wall.
Many edits, particularly regarding Laura.