Ross, son of ex - Aston villa player Andy Blair, was diagnosed with an incurable brain tumour in 2014.
The father-of-two is being cared for at the Myton Hospice in Coventry, where Holly has stayed with him day and night for a month.
Holly, who has also starred in Doctors and Casualty, has written a candid Facebook post as she sits as Ross's bedside in his final hours.
'What a reality to be waiting for one of the people you love most in the whole world to die and even hoping that it will come soon,' wrote Holly.
'That is a weird space to be in, but a space that I and his family are living in.
'Grieving before they have gone, waiting for the last breath, half knowing it's best if it is, half relieved when it's not.
'None of this feels real at all and I keep having moments of happend what the 'how did we even get here?!' Ross, who is just 32, was diagnosed with a rare grade-4 primitive neuroectodermal tumour (PNET), and underwent brain surgery and chemotherapy.
At the time doctors gave him the devastating diagnosis that he had a 50/50 chance of surviving more than five years.
But Ross, a property developer, responded well to the treatment and the tumour remained stable for two years.
Things looked hopeful, and the couple - who have been together for nine years - were able to continue lives as normal, making happy memories with their daughters Brooke, now six, and Texas, four. But in 2016 a scan revealed that the tumour had grown, and on August 4 Ross underwent a second operation at the Queen Elizabeth Hospital Birmingham, where 75 per cent of the tumour was removed.
It was followed by radiotherapy and a year of chemotherapy tablets.
Again, Ross responded well, and the couple were able to go about their lives as normal, enjoying making memories with their family.
In May the family travelled to the Caribbean for a holiday, where Ross was feeling good.
But just two days after they returned Ross suffered a seizure, and since then Holly said his health has rapidly deteriorated.
He was taken to hospital, then after a brief spell at home, he has been transferred to the Coventry hospice where Holly remains at his bedside. 'Nearly a month on, living in Myton Hospice and my amazing husband is still holding on,' said Holly.
'Of course he's now in a deep sleep, not eating, drinking, or conscious of his surroundings, but his strong body is fighting for him and sadly at this stage it is kind of working against him.