I definitely lean towards it being fabricated somehow. How did she make contact with this person and why them? Did she not try and ask anyone else these questions? I'm sure someone would have spoken up if they'd be approached.
What she wants us to believe is that she contacted one person from Tattle only to be interviewed, and that that one person agreed, and happened to have no opinion whatsoever on Sali's shilling, but instead disliked her because she was similar to a former friend?!
Very convenient.