Her 15-year-old niece in the front seat passed out from a serious concussion, but Ms Bell was in the most danger.
"My daughter was screaming from the back seat, 'mummy!' I was saying, 'I'm all right,' although I knew I wasn't.
"I realised I was trapped and I knew my leg was a mess. It was not pretty. I couldn't see where the dashboard ended and my leg began."
The children were taken away by ambulance, while Ms Bell was trapped for an hour, and the Warkworth and Wellsford fire crews used the jaws of life to cut her free.
But as she saw the rescue helicopter crew arrive, she knew hospital help was only minutes away.
"To see the red trousers and overalls appear was such a relief. I knew it was going to be over soon."
It was just 15 minutes to hospital in the helicopter, she said, where she was rushed into theatre.
"They saved my leg, I'm pretty sure," she said.
This month's annual chopper appeal comes just weeks after it was revealed the Auckland Rescue Helicopter Trust failed in its bid to overturn the Auckland Regional Amenities Funding Board's decision to slash their funding.
In March, the board voted to cut $450,000 from its support for the trust. It had cut a similar amount last year.
The trust had applied to the High Court at Auckland for a judicial review, but the bid was thrown out. Justice Susan Thomas said in her decision that "there was no actual evidence of the impact of the reduction in funding on its services".
Last year, more than 5500 missions were undertaken by rescue choppers nationally, with 923 in the Auckland region.
Auckland Rescue Helicopter Trust chief executive Greg Barrow said the service could not operate without support from the community.
"It's this generosity that allows us to carry out local rescue missions on a daily basis making a huge difference in many people's lives," he said.
He declined to comment on whether the donation drive took on added importance this year, following the High Court funding decision.
The Westpac Chopper Appeal throughout May is supported by open days at the helicopter bases, a variety of fundraising activities in schools and community centres, as well as a nationwide street appeal on Friday May 30.
Donations for the 2014 Westpac Chopper Appeal can be made at any Westpac Branch or at www.chopperappeal.co.nz. Westpac is the major sponsor of the Auckland, Waikato, Wellington and Canterbury Westpac rescue helicopters.
The annual Westpac Chopper Appeal helps raise funds for all regional rescue helicopter services around New Zealand.
