I think cOpying is alright up to a point,as a starter,
THEN ,why not copy two or three styles and then hybridise them.
Hoot,
I have carter family transcriptions[ by mike seeger,both of them have her playing in a piedmont style two or three fingers,with alternating bass],one is a 1930 the other a 1936 recording,the dvd is called carter guitar styles.
I would trust Mike Seeger to have got it right,maybelle may have later played it differently[thats possible]but at least two recordings having her play in the style of Lesley Riddle.