"My mother, she is 98. When she has naps and so on, she likes cuddly toys. So she sits there in the front seat stroking Tim the dead rat," Kelsey says. "Which is very sweet, and I don't have the heart to tell her that the rat is actually not very benign."
Mum is also the answer to a question about whether Kelsey's exhausting schedule allows for anything other than work and advocacy.
"She is the other thing. She lives in Mt Eden in a rest home there, so I take her out as much as I can," says Kelsey, who prefers to keep her focus on the issues, and agreed to this interview only after persistent requests.
Her life is "a bit chaotic" ahead of the TPP's signing in Auckland on Thursday.
Kelsey's brother, older by five years, is over from England to help pack up her Mt Wellington home, where she has lived since taking a job at the University of Auckland in 1979.
A retirement home at Algies Bay near Snells Beach is being built, and an apartment in the city bought - with a move-in date just five days after the TPP signing.
"In the midst of writing Waitangi Tribunal submissions and so on, last week the movers were moving stuff around me.
"It is a bit chaotic at the moment.
"The lovely old house I had just got too much - a quarter-acre section and so on - I just can't look after it any more. And it is time for me to start preparing for my retirement from the university."
That will be in five years' time, when Kelsey turns 65. She expects to continue as a professor emeritus, and the advocacy work that has made her an icon of the New Zealand left won't stop.
"But too many of my mates have been dying, so, it's, yes." She pauses. "There's more to life than being in the same house and the same job for the last 36 years."
Many of the faces arriving in Auckland ahead of Thursday's signing will be familiar to Kelsey, owing to her having racked up considerable air miles to be at TPP negotiations that have dragged on for five years.
The lovely old house I had just got too much - I just can't look after it.
She sat in hotel lobbies to pick up information when public stakeholder processes ended.
There's also domestic travel - when the Herald meets her at Parliament she's just off the plane from Auckland, in town for a media briefing organised by the Greens and to attend a town hall meeting, one of four around the country.
It's a schedule that elicits a wry laugh when Kelsey attempts to explain how she still teaches.
A newly acquired Marsden Grant will ease pressure, but recently it has been a case of squeezing in marking when possible, and paring down trips to lengths that most people would balk at.
"Often I will do a two-day trip up to the Northern Hemisphere and get off the plane and teach. The university has been good in helping me organise my time, because they see this as the legitimate part of my job."
A colleague says Kelsey is highly regarded, by both staff and students. "She spends a lot of time out of the country, but she's always present when she needs to be to teach and is completely reliable. I don't know how she manages it, personally, but she seems to."
Kelsey was born in Sydney. Her late father's job with the Tourist Bureau meant the family moved across the Tasman several times, living in Auckland, Melbourne and Wellington.
"He was the quintessential public servant who believed the role of people who worked for the government was to work for the public. So he instilled that belief in me," Kelsey says.
"I was always aware of policy issues because dad had to write answers to ministerials [questions asked by ministers] and so on. So there was always an awareness of the need for principled policy making."
After studying law at Victoria University, Kelsey completed a postgraduate law degree at Oxford University and a postgraduate criminology degree at Cambridge University.
Politics was a focus at Cambridge, particularly.
"It was the late 1970s when there was lots of international turmoil and it was in the era when you were having the transition to Thatcher ... and there were lots of debates about race, class, gender."
Back home, and aged just 23, she began teaching criminology at the University of Auckland, later focusing on the tensions between neoliberalism and the Treaty of Waitangi and other law.
An important moment came in 1990 while in Brussels where World Trade Organisation ministerial talks were taking place. An agreement on services was being negotiated, which Kelsey recognised as a way for corporate interests to remake and embed global rules in their interests.
Viewing the TPP as the starkest example of that pattern, Kelsey has paid for much of her international travel to monitor negotiations.
Research grant money has also helped, and support from the Law Foundation, provided on the basis that her work fostered public debate.
At the Greens' media briefing, Kelsey was joined by leading American TPP critic Lori Wallach, who delivered frequent media-friendly soundbites, including dubbing the agreement a "5000-page doorstop".
Kelsey's interview style is more a steely focus on putting arguments across without too much jargon or frills. TPP opponents loved her for it when she recently went up against Seven Sharp's Mike Hosking in a widely shared interview.
She is aware of the impression such fierce debate can give. Asked by the Herald photographer to smile, Kelsey, diminutive and dressed all in black, shot back, "I don't smile", her laughter then delivering the shot.
There's a need for some armour.
Groser himself has referred to TPP opponents as "irrelevant" and, in defending the secrecy of negotiations, said it was a job for adults, not "breathless children".
An old fur coat has provided Kelsey some revenge - even if her mum is herself a fan of Tim the Trade Rat.
