Alex, recruited to the campaign via a Facebook appeal, was eager to appear as - due to her age - her symptoms were initially dismissed by doctors. She is having chemotherapy and radiotherapy, but the disease has spread.
Alex, an IT analyst from Manchester, who appears with her mother Christine, 56, and her 19-year-old sister Phoebe, said: "I was shown the full script beforehand and I understood how powerful the words I had to say would be. I think their pledge to stop breast cancer deaths by 2050 is amazing.
"I don't think I'll be around at that point - but I really wish I could be."
Breast Cancer Now is a "super charity", formed from the recent merging of two existing charities, Breakthrough Breast Cancer and Breast Cancer Campaign in the UK.
Despite the positive intentions, Dr Charles Coombes, Professor of Medical Oncology at Imperial College London, and a leading breast cancer researcher, is sceptical.
"It's a nice message dreamed up by their PR team but it's very optimistic. We've reduced the breast cancer death rate by 50 per cent over the past three decades so if progress continues at the same rate you could say this would be achievable. But it's going to be more difficult from now on," he said.
"This advert should come with a warning attached. Women shouldn't think I can stop going to the gym and eating sensibly because Breast Cancer Now is going to have drugs for it. It's not just research that's going to help but changing lifestyle."
Lester Barr, consultant breast cancer surgeon at the Christie Hospital in Manchester and chairman of Genesis Cancer Prevention agrees. He said: "A cure is potentially achievable, but we have no guarantee so prevention is better in our view."
Breast Cancer Now insist the target is achievable.
"We believe 2050 is an ambitious, yet realistic goal," said a spokeswoman.
"Crucially, though, we will only be able to achieve this through the passion and generosity of our supporters and through collaboration with others: scientists, clinicians and the rest of the sector."
Alex was first diagnosed at the age of just 23 but she had been suffering with symptoms for three years.
"I first noticed a lump in my right breast when I was 20," she said.
"I was also getting discharge from my nipple so my GP referred me to a breast clinic for a check-up. I was given a physical examination but no scan and told I had lumpy boobs and that I could have an operation but I wouldn't be able to breast feed in later life, so I declined."
Over the next three years, pain in her armpit and breast got steadily worse and she went to a different GP.
The doctor sent her straight to a one-stop clinic where she was given a mammogram and a biopsy - and later the devastating diagnosis.
Her desire to help others by raising awareness of the early symptoms kicked in and Alex threw herself into writing a blog. It takes a humorous but honest look at her experiences and now has 4,000 subscribers. In March she learned that the cancer had spread to her bones but she hasn't asked doctors what her long-term prognosis might be.
"I've never asked and no one's ever said. I don't like words like terminal and palliative," said Alex.
"I do think the campaign has a realistic goal. They are making so many advances every week. As long as the money goes in to it I think they will get there. It's so important.
"So many people have breast cancer and too many are dying from the disease."
- Daily Mail