Woolf plays fast and loose with her narrative technique in A Room of One's Own (as she does in much of her other writing), so pinning the narrator down is tricky.
At first, Virginia Woolf is speaking as herself. Before long, the "I" becomes Mary Beton—but even that "I" isn't important: "call me Mary Beton, Mary Seton, Mary Carmichael, or by any name you please—it is not a matter of any importance" (1.2).
Why does Woolf choose to have Mary Beton in the picture at all? Wouldn't it be easier for her to just speak in her own voice and talk about her own experiences? After all, her experiences were pretty similar to Mary Beton's—just check out her "Character Analysis."
Well, Virginia Woolf knew the limitations of a first-person narrator: it's too easy for people to say that your experiences aren't universal. Enter Everywoman Mary Beton.