Can we equate the narrator’s voice with Welty’s?

In reading a piece of literature, one is almost always advised to separate the speaker or narrator from the author of the text. Even when the author and the speaker are indeed the same, the version of the author as he or she presents himself or herself within the context of a given text is still usually distinct from the author as a whole person.
In Eudora Welty’s “Why I Live at the P.O.,” Sister serves as the narrator who comes from a dysfunctional family of oddball characters in Mississippi. The central conflict Sister has is with her younger sister Stella-Rondo, whom Sister blames for both stealing her man (Mr. Whitaker) and thinking she is superior to Sister.
Welty was inspired to write this story based on a photograph she took while working for the WPA. The photograph depicts a woman using an ironing board in a post office. In light of these contextual realities, it would be a mistake to equate Sister’s voice with Welty’s personal voice.
Welty was certainly a Southerner, and her diction and character development are authentic aspects of her distinctly Southern realist style. However, voice typically refers to the persona behind what a character says. Welty is a skilled craftswoman who fleshes out a believable character in Sister, but Sister and Welty do not share the same narrative voice.