Fiona turned on her fellow Traitor during an explosive episode of the hit BBC show on Thursday (8 January).
The 62-year-old from Swansea accused Rachel of lying after the 42-year-old from County Down revealed Amanda's confession that she is a former police detective to the rest of the contestants.
However, Fiona refused to believe that Amanda would have confided in Rachel, saying she had “many family members who work in the police force."
Rachel then told the rest of the group that Fiona did not believe her, before Fiona announced that she believed Rachel was a traitor.
The interaction left fans asking what on earth happened, with one remarking, "This is television at its finest."
Read MoreSecret traitor reveal leaves fans convinced they could ‘win the whole thing’
Traitors contestant’s admission finally confirms fan theory
Dr Punam Krishan’s BBC colleagues send love after cancer diagnosis