"The P&O Ferry was lovely, just to set things straight, the people at the ferry border were horrible to me and to Toulouse and Sirius," she wrote.
Joan, who was later reunited with the dogs in London, complained that she had been prevented from getting on to the ferry for "no reason and against my will".
"I begged him to let me go through, he laughed at me and said no again ... I kept telling him and showing him again that the dogs were fully vaccinated and were 100 per cent vaccinated in order to enter the UK and then, I screamed," she wrote.
"I had done every ridiculous task he demanded of me ... and at this point he said he would call the police and have me arrested if I tried to go through... I told him to call them and to arrest me, because that was the only way I was not getting on the ferry."
She said that after running back on to the tour bus with the dogs, "suddenly, the bus driver appeared and said that there were men outside the bus to arrest me".
"I collected myself, took a deep breath and ran out yelling: 'Take me away with the dogs and I will sue you for abuse and harassment'... I told them that they were wrong, they were targeting Americans, they were abusing their authority ... they laughed.
"At this point, one man in a yellow jacket said to me, 'If you take the dogs, when you arrive in Dover, they will be killed!' ... I actually thought I disengaged from my body as tears started streaming down my face, and I felt as if I were losing my mind.
"I told him that they would have to kill me first and we would see what the US embassy would say about that."
Grande later tweeted in support of her mum.
"This was unacceptable. @poferries please have your employees treat people /animals with respect. Kindness goes a long way."
Mother and daughter were later reunited with the pets after the animals were assessed by a vet in the French town of Calais.
"The pups were safe and sound thanks to (half-brother) Frankie but it was indeed a terrible experience. No animal / human should be treated that way ... ever," the pop star said.
A spokesman for P&O Ferries has since issued a statement saying they "sympathise" with Grande's frustration but have defended the decision to deny the dogs entry into the country.
"The documents she presented were not valid to bring her pets into the UK.
"There are only two documents we can accept. One is a Pet Passport, the other is a Third Country Veterinary Certificate. The appropriate verification of treatments must be written into these documents."
Australian authorities threatened to destroy Depp's dogs after he failed to declare the Yorkshire terriers to customs when they arrived on a private jet.
He's currently in Australian filming Pirates of the Caribbean: Dead Men Tell No Tales, while the dogs have been sent home.
- PAA
