The actual question may have few true answers. I would agree that Eveline and Tina had a rivalry as they fought twice, both matches were fiery encounters.
At Festelle the rivalries between Maggie and Susan, and Ria and Susan spring to mind. They wrestled each other several times although always competitive never aggressive.
The three most aggressive ladies at Festelle Anita, Dani and Becky, as far as I know, only fought opponents once.
Rolling the years back to school days when girl fights seemed rare most were one affairs but there were, pairs of girls who had real rivalries who fought again and again and again.