Great find,
e_r, as it's yet more interesting than one might at first think:
Ruth Magnussen is evidently the daughter of artist
Gustav(e) Adolph Magnussen
http://bodegabayheritagegallery.com/...ave_Adolph.htm
About whom slightly conflicting info at:
http://bodegabayheritagegallery.com/...ave_Adolph.htm
and
https://www.askart.com/artist/Gustav...Magnussen.aspx
Checking through the CDs, I find (apparent typos listed as found) his addresses in LA as:
1900-1901: 344 S. Hill
1901: 402 Blanchard Music and Art Bldg., h[ome] 1355 Georgia
1902: 356 S Broadway, h 1705 Cherry
1904, 1905: 226 OT Johnson Bldg., h 945 W 36th
1906: 223 OT Johnson Bldg.
1907: 356 S Broadway rm 223
1908: 356 S Broadway rm 223, h 3809 Wesley Av
1909, 1910: 356 S. B’way rm 223, 3609 Wesley av
1911: 356 S. B’way rm 223, r[esidence] Eagle Rock av
1912: 212 W. 3d rm 400, Eagle Rock
1914: 145 S Spring rm 701, h 1466 Regent Lane
1915, 1916: 730 S Grand av rm 30, r 1466 Regina Lane
1917: 1466 Regina Lane
1918: 406 S Main rm 728, r 1644 Regina Lane
1920: 406 S Main rm 745
As we see, he was something of a wandering star in both his studio/office and his residence. But he was evidently only at Hafen House (344 S. Hill) when he first arrived in LA in 1900. I think it's likely that the two others on the upper porch are Ruth's (presumed) parents, her mother--
and the artist G.A. Magnussen.
_________
Edit add: Ruth, born in 1894, was Ruth Marie Magnussen. More about G.A. Magnussen (whose name is spelled a number of ways here and there in the world, complicating research) at:
https://ancestors.familysearch.org/e...ssen-1868-1944 .
His final address in San Francisco, according to the 1900 San Francisco Polk's CD, was 25A Belvedere St., which still exists (it was outside of the area of the fire).