Somehow a crisis in Barcelona was averted and the impromptu trip turned into a weekend in the sun with Savannah Marshall by her side.
Hunter will feature on the undercard of a BOXXER fight night in Newcastle on Saturday, live on Sky Sports, with Marshall defending her world title.
They hope it is less fraught than their last joint experience.
"We got a phone call 12 days out for a fight," Hunter remembers but her trainer was unavailable to take her, already committed with Liam Smith in Russia.
Hunter laughs: "I took it anyway."
Marshall recalls her invite on a trip that was pitched as a no-risk trip to Barcelona: "I thought: 'Jackpot! A little holiday!'"
Marshall then realised she was the only person alongside her friend, who was in just her third fight.
"She told me her coach wasn't coming," Marshall says, still shocked by the memory of her newfound responsibility. "I did tell her that I don't know how to wrap hands or do cuts."
Hunter roped in an old amateur coach who she hadn't spoken to in years but, at late-notice, he wasn't allowed in her corner.
This is where Stefi Bull comes in - awkwardly, just a week earlier Hunter had been sparring with world champion Terri Harper, who is trained by Bull.
Bull was in Barcelona alongside Gavin McDonnell, who was fighting on the same bill, but rose to the challenge of helping Hunter who was trading punches with his prized asset just days prior.
"You couldn't write it," cringes Hunter.
Perhaps the signs of disaster were there. Making weight abroad for the first time, she was advised to eat cheese and wash away the salt from peanuts to help the process.
"I don't know!"
Hunter says: "The day before my fight. Who turns up with an England flag which says 'Team Hunter?' It's Joe Laws! He took two flights to get there. He was wearing a white Adidas vest, flip-flops, shorts.
"Twenty minutes before my fight, Sav says: 'Joe is on the phone and doesn't have the address to the venue!'
"I said: 'I'm not bothered right now!'"
Marshall recalls her own worry: "I was sat with her in her changing room. I asked: 'April, have you put Vaseline on yet?'
"I said: 'Can somebody please put Vaseline on her!'
"I don't know how her nerves coped."
Marshall, not allowed to be in the corner, sat in the crowd and was texting back and forth with Hunter's trainer. When he sent instructions through, she would shout them to Hunter in the ring.
"Even the fight had its ups and downs," Hunter says.
"In the first round I hit her with a left hook and thought: 'Early night!'
"I got too excited, tried to steamroll her, and got clipped myself."
She beat Elsa Hemat via majority decision, making the entire trip worthwhile. It meant the next few days could be spent enjoying the Spanish sunshine.
"It was like a girls' holiday!"
Hunter was a footballer on Newcastle United's books until a terrible knee injury curtailed that dream.
She had always excelled at sports: "My teacher told me: 'You are the most gifted female sportsperson we have ever taught - whether it's football, badminton, anything."
She was "aggressive, relentless and skilful" as a central midfielder and was a regular at St. James' Park: "I was there in the Kevin Nolan era when we beat Sunderland 5-1!"
Injury cost her a football scholarship in America and, instead, she fell into a cycle of socialising to excess.
"I put weight on so went to the boxing gym," she says.
"My first session I was sparring with the lads. The coach said: 'You have talent, please come back'.
"Being in the gym with lads, you have to push harder. When you get the better of them? You know you are firing."
Hunter is now part of an emerging crop of talented fighters in the women's boxing scene: "Where it's at now, compared to where it was, is unbelievable. Katie Taylor paved the way but now we have Savannah Marshall who I think is the best female boxer on the planet.
"We need the first female major fight. I think it will be Marshall and Claressa Shields. I hope Claressa wants it but I think she's ducking Sav.
"Claressa knows how dangerous that fight is. Sav will hit too hard and be too strong."
Jessica McCaskill is the undisputed welterweight champion in the division that Hunter is eyeing.
"She is relentless, crazy work-rate, very fit and strong," Hunter says. "But I don't think she's a great boxer.
"In women's boxing there are very few boxers who actually think and set their shots up. They don't set traps. This is what we are working on.
"I'm not that far off McCaskill."
Hunter can extend her winning record to 5-0 on Saturday and intends to become a world champion within 18 months.
October 16 - Top Rank in San Diego
Emanuel Navarette vs Joet Gonzalez - WBO featherweight title
October 16 - BOXXER in Newcastle
Savannah Marshall vs Lolita Muzeya - WBO middleweight title
Hughie Fury vs Christian Hammer
Chris Eubank Jr vs Wanik Awidjan
Lewis Ritson vs Hank Lundy
October 24 - Top Rank in Atlanta
Jamel Herring vs Shakur Stevenson - WBO super-featherweight title
October 31 - Top Rank in New York
Jose Zepeda vs Josue Vargas
November 6 - Top Rank in Las Vegas
Mikaela Mayer vs Maiva Hamadouche - IBF and WBO super-featherweight titles
November 6 - BOXXER in Liverpool
November 20 - BOXXER in London
Richard Riakporhe vs Olanrewaju Durodola
Caroline Dubois professional debut
November 20 - Top Rank in Las Vegas
Terence Crawford vs Shawn Porter - WBO welterweight title
December 11 - Top Rank in Las Vegas
Vasiliy Lomachenko vs Richard Commey
December 17 - Top Rank in Montreal
Artur Beterbiev vs Marcus Browne - IBF and WBC light-heavyweight titles
December 18 - Top Rank in Glasgow
Josh Taylor vs Jack Catterall - undisputed super-lightweight title