Isaac, who served a UK prison term for the possession of ammunition and was friendly with some of London and Manchester's most feared gangsters, suffered the fatal injury after clambering onto a wheelie bin so he could get through a first floor window of his Dromreagh home.
Isaac, who was 6ft 4in and weighed over 18st, fell and jammed his neck between a wall and bathtub.
His body was only discovered by gardai after a workman raised the alarm.
Ms Ginty was visiting relatives in the UK when the accident occurred but has returned to Ireland to finalise his funeral arrangements.
"People judged him by his appearance and by his past. It was very unfair. He wasn't at all like the way he is being painted in the media," she said.
Ms Ginty told the Herald that his body will be brought back to his native Manchester so he can be buried beside his mother.
"The underworld, the boxing world and and people in different places have been affected by this and everyone is in deep shock," she said.
"His close friends, his ex-wife and myself are all in shock. He just had a really big heart. He just wanted to help everyone all the time. He was non-stop, he was 100-miles-an-hour. If you needed anything, he would go out of his way to do it."
They had planned to get married in the New Year.
"A lot of people thought a lot of him in so many different worlds – boxing, greyhounds and the other side of his life.
"My family thought of him as family. We've lost the link that kept everyone together," she said.
"Not many people in Ireland got to know Billy on a personal level. But I can assure you the ones that did thought a lot of him and wouldn't have a bad word to say about him. Don't judge a book by its cover."
She also denied that Isaac's decision to call their isolated home 'Ratsville' or decorate the gate and railings with rodent designs was in any way sinister.
"It was an affectionate, personal joke between us ... nothing more than that," she said.
Isaac, whose intimidating appearance was made all the more ferocious by three gangland-style teardrop tattoos under his left eye, was acquitted of a gangland-style murder in the UK in 1995.
He was also cleared over the next decade on various charges of assault causing serious harm, blackmail and intimidation.
In 2010, was also acquitted of threatening to kill an English businessman's wife and children if he did not hand over £2.5m (€3m).
The acquittal came after he received a glowing character reference from former world champion boxer Ricky Hatton.
Last month, Isaac was given a five-month prison sentence in Bantry District Court for his role in an assault on a petite waitress in a Durrus bistro.
He died while on bail pending an appeal against the severity of the sentence.