''I asked Mum if I could still eat it and she suggested we send it back to the factory.''
Upset at the quality of the product, she wrote a letter of complaint to Cadbury Fry Hudson Ltd (as it was known then) in Dunedin.
And in response, she was sent a letter from the company, which reimbursed her with another block of Cadbury peppermint chocolate, the 5c cost of postage for her original letter, and the offer of a free tour of the Dunedin factory to see how the chocolate was made.
This week, nearly 50 years after receiving the offer, she travelled from her home in Whanganui to take the tour.
''My daughter finished university, so I've come down and I've bought a van in Dunedin, and we're taking all her stuff back up to the North Island.
''I haven't been here since I was 8. I've never really had an opportunity to come back and cash the letter in.
''I'm sorry to hear the factory is going. I thought, if I don't do it now, I'll never get another chance.''
Bethell said the tour was ''marvellous''.
''They [Cadbury] gave myself, my partner and my daughter a free hot chocolate and a free tour of the factory.
''I felt like Charlie with his golden ticket.''
She said the van ride home would be arduous, ''but at least we'll have plenty of chocolate treats to munch on on the way back''.