The dive had fractured the C5 vertebra in Ms Boyd's neck.
The mother, who has one son, was taken to Christchurch Hospital, where she remained in the intensive care unit for about a week.
She has since been recovering in a rehabilitation centre in Christchurch. Doctors do not know whether she will walk again.
"At the moment she can move her arms and her head, but she's in a neck-brace and she can't move her legs yet.
"There's no feeling in her legs."
Ms Farrell said her friend was too upset to talk about the accident but remained talkative and was being strong for her son Willie, 4, who is staying with his father in Auckland.
"I went to see her and asked her: 'How can you be so positive right now?'" Ms Farrell said.
"She's amazing."
She said the idea of her friend not being able to walk again was a hard one for her to take, given Ms Boyd had always enjoyed playing sport, particularly volleyball.
In 2004, Ms Boyd captained the New Zealand women's under-19 volleyball team.
She has also played for a number of teams in Auckland and in the Bay of Plenty - she was born and raised in the settlement of Omaio, east of Opotiki.
She stopped playing competitively this year and until recently worked as a bar manager.
Family and friends have rallied around the young mother, who is being helped by her brother Eric.
They have set up a fundraising page for her on the GiveALittle website.
Ms Farrell said the money raised would go towards helping to pay for medical bills as well as for Willieto travel back and forth to see his mum.
Teina Boyd
*Age: 28
*Former NZ representative volleyball player
*Captained the New Zealand women's under-19 team in 2004
*Fractured the C5 vertebra in her neck in an accident
*Doctors do not know whether she will regain the use of her legs
