I didn't know how much information you have on this woman so I did the research below. Sometimes people seek obits more to try to find where the persons family was at the time. I did not find any information as to why this person died in Angwin per your information, if she was living there or just passing through. I found none of her family after 1930 or if she had remarried between 1930 and 34, thus potentially giving her children a foster/adoptive parent.
The 1930 Census of Santa Rosa, Sonoma Co, CA, enumerated April 18.
Anna Righetti, age 28(1901/1902), born in CA to both parents born in Switzerland, first married age 16(1917/1918). Widow.
Fred, son, 10 (1919/1920)
Donald, son 5 (1924/1925)
Antoinette Zappa, age 58, widow.
The 1920 Census of Santa Rosa, Sonoma Co, CA
Antonia Zeppa(as transcribed) (Antonie Zappa, as amended), age 34, born in Italy, immigrated 1890/Alien
Giacento Zappa, 16 (1903/1904)
Maggie Zappa, 14(1905/1906)
The 1920 Census of Santa Rosa, Sonoma Co, CA, enumerated 3 January.
L. M. Righetti, age 26(1893/1894), born in CA to both parents born in Switzerland
Anna, 19(1900/1901), born in CA to both parents born in Switzerland
--both parents spoke Italian.
--based on enumeration dates of the 1930 and 1920 census, Fred appears to have been born between 3 January 1920 and 18 April 1920.
--CA Birth Index shows Donald Kearny Righetti born 25 June 1925, mother's maiden "Zappa." Born in Sonoma Co. www.zabasearch.com
shows a Don Righetti in San Luis Obispo. (However documents show he is 59).
WWI Draft Registration:
Leno Marion Righetti, born January 10, 1893 in Bodega, CA, working as a waiter/cook in Santa Rosa, CA. Single. Registered on June 5, 1917.
WWII Draft Registration:
Leno Marion Rghetti, born Jan 10, 1893 in Bodega, living in Yountville, Napa County, CA. He was 5'-8 1/2" in height, 144 pounds, blue eyes, gray hair.
--So Mary was not a widow in the 1930 Census. This was common then.
--Leno died 26 Mar 1977 in Napa Co. His obit might be a source of information also.