That is very interesting. I took the 1910 census transcription as a mistake when in fact it could be accurate.
The 1910 census and death of Sallie Jane ties Mattie into father James and mother Ann Holly.
Erkwood is Bernard Erkwood and he married Cecelia Pickering(my relative) 21 Nov 1932 Los Angeles.
Mattie would have gone to California after 1941 since she was still living in Birmingham.