Pamela was adopted by the childless Edward and Gladys Werner when she was an infant.
ETC Werner described next to nothing about her adoption, the legal process for which was far less formal than that of today.
If her (given) birthday was correct, Pamela was born in January 1917. There is no trace of the Werners travelling abroad during the immediate years thereafter so the likelihood is that Pamela was adopted locally. It is also likely that she was born to a "White Russian" mother, which may have been another reason for silence on the matter.
China had long been home to many Russians. After the 1917 revolution it became home to tens of thousands more as White Russian opponents of the Bolsheviks flooded into the country as refugees.
Though some were of aristocratic background, the great majority soon found themselves poor white immigrants in poor country. They were destitute. Adoption for Pamela may have been the best option for her.