Answer: twinsister

AnswerCrossword Clue
TWINSISTERAnn Landers or Abigail Van Buren
TWINSISTERShe may be fraternal
TWINSISTERAnn Landers, to Abigail Van Buren
TWINSISTER"Identical" sibling
TWINSISTERLanders' Abby, e.g.
TWINSISTERFraternal one, perhaps