Last filmed an emotional goodbye video for her 15,000 followers on her beauty vlog that focused on makeup for older women.
"It's been amazing, I've loved every second," she said with tears running down her face.
"It's not going to get better. That's what I am coping with at the moment. I can't hide it any more."
She apologised for what had happened to her and the message she was giving.
"I am so sorry this is such a horrible message. But I wanted you to share the final part of my journey," Last said.
The eight-minute farewell video has been watched more than 75,000 times so far.
Doctors discovered a mass on her brain and further tests revealed that she had a brain tumour affecting her occipital and parietal lobes, which control vision and language processing.
Further scans showed that the beauty blogger could not be treated.
"She called me and said 'I've got some news'," her husband, David Last, told The Sun. "'They can't do anything for me'."
Last's four children have tried to remain cheerful for their mother's sake but her memory and speech are deteriorating.
Her husband wants to raise money to take her to Agatha Christie's beach house in Devon, and for funeral costs.
Revolution Beauty founder Adam Minto has already offered support after hearing her terminal diagnosis.
