Their relationship is sometimes referred to by the fan-given nickname Keddie Or Fratie.
Series 3EditBy the events of "Effy", Katie has become the Queen B of the school; something she loves to rub in Effy's face (along with her new relationship with Freddie). Wanting to be even more popular with the gang, she brings up the idea of going on a group camping trip (however, she is quite annoyed when Effy is invited). Everything seems to be going in Katie's favor, until Effy brings out some shrooms that she had brought. This makes Effy popular again with the gang, much to Katie's chargin. Throughout the night, she feels like Freddie's feelings are waning and he rebuffs her when she tries to display their relationship in front of Effy. When an uninvited Cook crashes the party, Katie seems to be the only one that liked him being there, because she was able to remind Freddie about Cook's relationship with Effy. Later that night, she follows Effy into the woods (not knowing that Effy is high). she confronts Effy about Freddie, and after pleading with her (asking Effy to please give her Freddie as that is the only thing she has); she attacks her, telling Effy that she will never take Freddie away from her. Effy, starting to experience a bad trip, freaks out and hits Katie in the head with a rock, knocking her unconscious. The next morning, the gang realizes that Katie is missing but assume she just went home early (given her unhappy mood the night before). Katie is eventually found and taken to the hospital, where she wakes up and tell the gang what Effy did to her (but not about her own involvement), thus turning everyone against Effy.
With Effy gone, Katie feels that she no longer has to worry about Freddie leaving her, however she comes to the realization that he still is in love with Effy. With Emily and Naomi's relationship on the rocks, Katie decides that she and her sister will go on a double date to the school dance, with her going with Freddie and Emily going with JJ.
During "Freddie" Katie is seen at Effy's "goodbye" party, annoyed and stating that she doesn't party with goths. Later, she is seen being a dancer on a float during the Judgement Day parade. Seeing a freaked out Effy, she pulls her out of the crowd and signals for Freddie to get her, as Effy was unable to calm herself down. She later accompanies Effy and Freddie to visit his grandfather. She notices Effy had been gone a long time and goes to check on her. When she can't open the bathroom door, she runs and tells Freddie (who goes and breaks it down).