For Carter Family songs like Gospel Ship, she'd pick the tune and runs with her thumb and strum chords with her fingers (Carter's Scratch)
She would use a Travis-style three finger picking both with thumb lead (Butcher Boy) and finger lead.
For ballads, she would often use a four finger arpeggio style:
TIMRMI or TIMIRIMI or TIMIRIMI or some other patterns, usually starting with the thumb. She would sometimes use what Peggy Seeger called the "lullaby lick" in 3/4 and 4/4.