Mr Bisman said Charlotte had been recovering at home after undergoing surgery a week ago. "It's been a hard road.
"She's had two major operations - we figured out that the last one was her 22nd operation - and she's been quite sore."
Going to the Nitro Circus show - where BMX riders perform tricks and jumps in front of a large crowd - was something of a reward for her.
"She's a total petrol-head."
Charlotte became a fan of the Nitro Circus after being introduced to it by her best friend, 9-year-old Rhythm Lewis.
Rhythm's mother, Lani Lewis, said the pair had been good friends practically their whole lives and were both pupils at Waiheke School.
Rhythm had organised tickets for he and Charlotte to attend tomorrow's show, but were disappointed when they realised they would not be given wheelchair access, meaning Charlotte could not go.
Ms Lewis said: "It was Rhythm's idea that we email the organisers and ask for a favour. He felt really sad he wouldn't be able to go with Charlotte so wanted to try and get her to the show."
The show moves on to Hamilton and Wellington next week.