Songwriters Tommy Dunbar and James Gangwer filed the suit after spotting striking similarities between her tune and the 1979 Runbinoo's song 'I Wanna Be Your Boyfriend'.
The pop star's manager Terry McBride has had musicologists study the two singles and denies any wrong doing by the Canadian singer, commenting: "Avril's a great song writer and she's proving it over and over and over again."
He added: "Avril's very, very sensible. She knows music well. If the chords had been similar, the melodies had been similar, lyrics had been similar, the meter, she would have gone, 'Okay, I can see their point.' But nothing's similar."