Barbara Lynn, from the 1966 Dallas TV show The !!!! Beat:
It's a weird guitar style alright, left-handed and mostly hitting the strings on the upstroke, but she can really play that thing: check out "What'd I say" from the same show, with Clarence "Gatemouth" Brown.
"You'll Lose a Good Thing" was originally a hit in 1962, co-written by Lynn and New Orleans producer Huey P. Meaux.
She's still going strong. Yesterday was her 72nd birthday.