"She had a critical car crash just before the Wairoa Bridge and lost her kneecap," Bella said.
The 11-year-old was "passionate" about making SH2 safer.
"Every time anyone drives on SH2 they always have a chance of being in an accident," Bella wrote in her letter to Warren-Clark.
She suggested a roundabout at the intersection of the Omokoroa turn-off so motorists would "take notice of who's going where", which would hopefully reduce the number of injuries caused by crashes.
About 30 letters had been written and would be sent later this week.
Year 7 and 8 teacher Deb Warren said she had given pupils three options of representatives to write to; Ardern, Warren-Clark or NZTA.
"They [pupils] have come up with some interesting ideas and have done their own research," Warren said.
Pupils were told to write constructively rather than complain about the highway in order to be heard.
Liam Burston and Elias Cresswell joined forces to write to NZTA.
They suggested a roundabout or flyover at the only road into Omokoroa.
"Getting on to SH2 takes a lot of time and is really dangerous," Liam said.
Patrick Farrell's idea of a new road was addressed to the Prime Minister.
"I wrote the letter to the Prime Minister because she holds the most power," Patrick said.
Manager of the Prime Minister's correspondence unit, Dinah Okeby, said the Prime Minister would be reading the letters herself and the students could expect a reply from her.
She said the number of letters and emails Ardern received from young New Zealanders varied.
"At the moment we have over 100 letters from students from five different schools in the office and several more from young people who have written to the PM individually."
Kids have their say
"A roundabout at the entrance of Omokoroa and SH2 so people will go slower and take notice of who's going where so we can decrease the number of injuries and deaths each year."
- Bella McShane, 11 "There could be changes like a roundabout or a flyover. These may take a while and cost a lot of money but our lives and the lives of New Zealanders are worth more than money can buy."
- Liam Burston, 12 "Only a little while ago residents of Omokoroa had a debate meeting for ideas on how to make a difference and save lives. Most people came out angry."
- Elias Cresswell, 12 "With planning, a new road can be built to reduce traffic and the death toll of SH2. According to our knowledge, the road would be called the Northern Link."
- Patrick Farrell, 12
