It's a bitter memory that refuses to exit her head.
The unbeaten Rousey, who now rules the UFC women's bantamweight division, did what she does best. The former Olympic judo bronze medallist got her mitts on Kaufman at the fence and took her down.
Kaufman fought off Rousey's signature armbar move several times, but eventually had to tap.
It took just 54 seconds.
"I think for me the biggest disappointment in that fight was that I didn't fight," said Kaufman, who described herself as "extremely embarrassed" at the post-fight news conference. "To me it wasn't even a fight. I could have had zero training and probably fought better.
"I don't know why I fought like that. I've thought about it a lot ... at the end of the day it's fight, it's a minute. It was a minute out of my life that changed my career a lot. I do think about it a lot, but again there's not much that I could (do) — well there's nothing I can do about it."
The 28-year-old from Victoria makes her UFC debut Saturday against Jessica (Evil) Eye at UFC 166 in Houston. Cain Velasquez defends his heavyweight title against former champion Junior Dos Santos in the main event at the Toyota Center.
Eye (10-1) is also a UFC debutante.
Kaufman (16-2) returned to action in April, winning a split decision over Leslie Smith on an Invicta FC card in Kansas City.
While ranked second among UFC female welterweights, the Canadian has had to wait her turn to step into the Octagon.
She was slated to make her UFC debut against No. 4 Sara McMann in August in a televised card in Indianapolis, only to have her opponent drop out just days before the fight.
Kaufman is the last of the UFC's top-10 contenders in the women's 135-pound division to make it to the Octagon. In fact, a dozen women have fought ahead of her, with some having already done so twice.
"It's been frustrating watching all these other girls step in," said the five-foot-five Canadian.
For Kaufman, fighting is the exciting part of her sport.
"Training's hard, training's rough. There's definitely days where you're like 'This is awesome.' Then there's other days where you're like 'This is the worst, why do I do this?' I think that's part of the sport. The highlight is the fighting."
Kaufman already has beaten three of the other top 10 contenders — Liz Carmouche, Alexis Davis (twice), and Miesha Tate — outside the UFC.
And a win over Eye on Saturday could put her in a good position with No. 1 contender Cat Zingano sidelined by injury. UFC president Dana White says he is in a wait and see mode with Zingano's health.
Rousey and Tate, featured as rival coaches on the current season of The Ultimate Fighter, are slated to meet Dec. 28 at UFC 168.
Kaufman is ready and willing to step in as needed. But she believes her standup skills have made her a less than desirable opponent to some.
"A lot of people don't mind getting wrestled or getting tapped out if that happens," she said. "But a lot of people don't really like getting punched in the face. And I think when people fight me they know that is a strong likelihood."
Kaufman, who had her first pro fight in 2006, grew up a dancer but found her way into MMA at 17 when Adam Zugec opened a mixed martial arts school in the building where her dance company rehearsed.
She signed up for a women's Muay Thai class and then found she wanted to learn more.
Today, Zugec is a coach and trusted friend who corners her at every fight. And Kaufman trains and teaches at his Zuma gym. She also spends time in Albuquerque training under Greg Jackson.
Kaufman's students range from the Canadian women's rugby team — wrestling technique isn't that far from tackling — to the "little bulldogs" aged three to five.
"The cutest things you've ever seen," said Kaufman.
She teaches Monday through Saturday, fitting training sessions around her classes. On Sunday, she goes for a leisurely run.
There are no airs surrounding Kaufman, a former Strikeforce title-holder herself. Her championship belts are discretely tucked away on a shelf at the gym and Kaufman is not averse to taking a mop to the wrestling mats when needed.
She is not used to having time on her hands and admits she is at a loss on holidays and rare days when her schedule isn't full.
"It's 4 o'clock, what do people do between now and midnight," she recalls thinking.
"I don't know what normal people do."
Single, with a dog named Rhino, Kaufman lives in a nearby condo and drives a second-hand Nissan Ultima with more than 180,000 kilometres on it.
"I'm not into spending money in general, but especially on cars," she explains.
Her history is checkered with vehicles. A Firefly was junked after she drove into the gym, the car careening down a steep hill after she spilled a tea she was bringing Zugec.
Analytical by nature, Kaufman tends to break things down step by step. It can be a hindrance in the cage.
"I just need to fight a bit more and less analyse," she conceded.
Kaufman is hard on herself, which helps explains why the Rousey loss hurt so much.
"That's why that one just boils in my stomach a little bit."
She was in the gym the day after the loss, albeit with a slightly modified routine to protect a sore arm that had been twisted the wrong way.
"It's crazy how something so fast can still do quite a bit of damage," Kaufman said.
She walks around at 158 pounds, trimming down to around 148 for fight week and then cutting to 135 for the weigh-in.
Kaufman eats clean. A typical day might include yogurt and oatmeal with cinnamon for breakfast and chicken and spinach salad for both lunch and dinner.
A rare treat may be a handful of chocolate raisins.
Outside the cage, Kaufman is personable and not afraid to speak her mind.
When she was fighting on Strikeforce's secondary Challengers card, she wondered publicly why women were not being showcased on the main cards.
And when Strikeforce played up the sex and sizzle of the first Rousey-Tate fight, she asked why not let the fighters' talent speaks for themselves.
It's still early days for the UFC women's division, but Kaufman is happy that fights and not hemlines are grabbing attention.
"You're starting to see, which makes me really happy, a departure from just this girl's really hot and can fight to look at her personality, look at her knowledge base, look at her personal life," she said.
"Everyone kind of has their own thing and I've been trying to say that for years that I shouldn't, it's just not me, to wear little mini-skirts and half-tops. That's just my personality.
"Even as a kid, I didn't like wearing skirts. So I think it's so great to now see that people's personalities are starting to come out and they're getting valued for what they're able to do as opposed to what they look like or how they want to portray themselves."