Dear Papa will not salute the Stars and Stripes. “An Edgefield man would die first,” Papa says. Yet he doesn’t like it when Mama quotes Mark Twain, who has recently written that Old Glory should be changed to a pirate flag, with black stripes and each star a skull and crossbones. As long as this great land of ours is fighting, the men aren’t fussy about who they fight -- this is Mama talking with her small bent smile. Papa smiles, too, but he is wary. Mama’s needles fly as she quotes from an editorial read at the library, “The taste of Empire is in the mouth of the people, even as the taste of blood --‘”
(Killing Mister Watson, by Peter Matthiessen)
‘This’ seems to refer to the anterior sentence, 'As long as this great land of ours is fighting, the men aren’t fussy about who they fight.' And the head of predicative complement, which is ‘Mama talking with her small bent smile’, is ‘talking.’ However, the modifier of ‘talking’ isn’t possessive case, Mama’s. Can we say both ‘this is Mama’s talking’ and ‘this is Mama talking’? Or is there any other reason to say that way?