Six-year-old Roxy suffered a fractured pelvis, bruised heart and internal bleeding.
The first helper, Christian - who did not want his surname used - stopped when he saw Roxy injured on the side of the highway and took her to the vet clinic, paying the money before he left and without telling Kiddle.
That $1500 went toward the blood transfusion and other life-saving treatment needed to stabilise Roxy that night.
Christian, 29, told the Herald on Sunday the money came out of savings for his overseas wedding in June and he didn't expect Kiddle to pay it back if she couldn't.
"I love dogs. I'm more of a dog person than I am a people person if I'm honest. They bring a lot more joy to my life and I just did what I thought was right. I'd do anything I could to keep the dog alive."
Then, the Auckland couple, who wanted to remain anonymous, also took money out of savings after reading about Roxy's plight in the Herald on Sunday, according to Kiddle.
"They said, 'We don't want to hear that something has happened to her because time and money have been the issue'."
They loaned her the $13,500 to pay for the rest of the treatment and Roxy was able to return home on New Year's Day.
A Facebook page Kiddle set up just before Christmas to raise money for the surgery had so far netted about $5000 but Kiddle said Facebook had yet to release the funds.
She planned to continue the effort to raise the entire $15,000 to pay it back and was hopeful of more money as well as any donated goods and services for an online auction she planned to set up.
Animal Referral Centre vet Dr Fiona Park said on the night of admission, Roxy was given essential treatment including pain relief and oxygen, with an initial estimate of $1500 for the treatment.
However the following day it became clear Roxy needed ongoing intensive care.
"Once Roxy was stable enough to undergo imaging, a CT scan was performed that showed severe multiple pelvic fractures requiring surgery as well as signs of bleeding from one of her kidneys."
Park said the vet hospital owners agreed to "cap" Roxy's bill at $15,000 despite estimating the true cost of treatment would be $20,000-$25,000.
"Although this seems like an astronomic figure, it is not typical of treatment costs for most animals, even in a veterinary specialist hospital such as Animal Referral Centre."
She called Roxy's injuries "extremely severe", and said multiple surgeries and extended hospitalisation were required.
"Roxy is lucky to be alive. Before the availability of veterinary hospitals with specialist staff and 24/7 care, it would not be possible to have a successful outcome in a case like Roxy's.
"For pet owners who elect this level of care, there are alternative options for helping with payment, including finance plans and pet health insurance."
To donate toward the cost of Roxy's surgery visit the Save Roxy page on Facebook.