The couple are living in Adelaide but will return to Auckland for the launch, where supporters are being asked to wear turqouise, the teen's favourite colour.
Mrs Marceau said returning to Auckland and the still-raw memories of Christie's death would be hard. "It's going to be a really traumatic time for us.
"But the fact that we've got so many people behind us, I really need to see them as well, to thank them. I really can't believe what people have done for us, to be honest. I've been just blown away; it's beyond words."
Mrs Marceau believes a law change would save lives. It would also give victims of violent crime more protection and peace of mind.
"I want people to think that they're going to be safe. I also want everybody who has a child in New Zealand to hug that child ... and just be thankful that they've still got them.
"Because I tell you what: it's so hard to sit there and think that I will never ever see her again. All I've got is photos and videos."
Mrs Marceau hopes that every time people think about Christie's Law, "they see her face. And, they realise just how brave she was with what she endured."
"That's what I want people to remember - just what a loss she has been. Not just to us but what a great contribution she would have made to New Zealand. We can't afford to let people like that go ..."
Mrs Marceau said she was starting to feel settled in Adelaide - but she was still shattered by the death of her "princess".
"I knew that things would be a lot different in Adelaide, without the memories. It has helped to that extent, but it never goes away.
"I find it quite hard when I walk down the street and see girls Christie's age. I was in a mall the other day and I heard somebody call out, 'Mum'. I turned around because I thought it was Christie ... It was really gut wrenching. She should still be here. And, she was supposed to have arrived last weekend, so that was really difficult."
Christie had planned to move to Australia, where Mr Marceau was working, with her mother and enrol at university. She had just finished her first year of uni in Auckland when she died.
Mrs Marceau said organising the campaign had been a good way to keep her mind off the horror of Christie's death.
"We know that Christie is giving us strength. I can always feel her. She'd be proud of what we're doing.
"If things had been the other way around, she would have been the first out there trying to help.
"For me, it's got to succeed. We've lost our daughter ... but there's no way I'm going to let people forget her."
The campaign
The Christie's Law campaign will be launched at the High Court at Auckland on Monday, February 27, from 11.30am. The Marceau family have asked supporters to wear turquoise as a tribute to Christie.
Donations
To Christie's Law Trust at Westpac, account number 03-0275-0644809-00.
