"I'd just arrived at Sea View and was being introduced to the animals when I went into the cat enclosure.
"There were four, 9-month-old lion cubs and one of them, Carrie, just came running up to me and bit me on the breast.
"It didn't pierce the skin but I was a bit shocked and shaken up because she was so enthusiastic. She hung on there for a few seconds but I had to shove her away to get her off.
"During my stay there, Carrie wouldn't leave me alone ripping my shorts, going after my shoe laces. It was only after 10 days that she calmed down and accepted me and when you think that a 9-month-old lion cub can weigh between 80 and 100 kilos, that's a lot of animal."
Weeks later, after returning to the UK, Ms Krivan checked the mark on her right breast where Carrie had bitten her and noticed a lump.
"I just thought I was too young to get cancer because I was only 30."
But doctors found the lump was cancerous and she had surgery four days later.
The surgery was followed by chemotherapy and radiation treatment and she is now in remission, undergoing checks every three months.
"Being told it was cancer was the worst day of my life. Having to phone my parents back in New Zealand was awful because they felt so helpless.
"I just couldn't believe it was happening to me. Fortunately it wasn't an aggressive form of cancer but it was still stage two grade two.
"I lost my hair, suffered from extreme tiredness, insomnia, ulcers and just felt awful. It was a bad experience."
Parents Janet and Ross from Tawa travelled over to the UK a week later to help her recovery. More than 18 months later, she is back working full-time but has to take Tamoxifen drugs for the next five years.
She decided to speak about her experience as part of the UK's October Breast Cancer Awareness month and to praise the support she received from the Haven and Breast Cancer Care support centres in London.
Ms Krivan, who attended Tawa College and then Victoria University in Wellington, where she studied for a business and commerce degree, said: "I don't know if Carrie knew I had cancer. I've heard of dolphins identifying cancer and cats and dogs lying next to ill people but I don't know about lions.
"At the end of my time at Sea View, I spent hours and hours with Carrie and we had a strong bond, which is obviously stronger now.
"Without Carrie biting me there, I probably would never have known to check my breast ... I'll always be grateful to her."
Ms Krivan is now planning her return to New Zealand with boyfriend Craig, from Shannon, but will always worry the disease may return.