TV presenter Phillips, 62, told fans this week that she had been diagnosed more than a year ago, leading to an outpouring of support from her celebrity friends, colleagues and fans.
Speaking on Good Morning Britain, Garraway shared that the last time she spoke to Phillips it was about her own husband Derek Draper, who needs round the clock care after spending a year in hospital battling COVID.
"The last conversation I had with her, which was only a few weeks ago, what she was doing was talking to me about Derek – full of love for Derek, very close to Derek – and thinking about me dealing with Derek," she said.
Garraway went on: "Of course, I now think that she must have had in her mind that she would come to a place where Martin and her sons were going to be taking care of her.
"It just makes me feel emotional thinking about how that must have been going through her mind.
"And still is."
Phillips told the Mirror that she was diagnosed after suffering “brain fog and anxiety”.
She had thought the symptoms were linked to the menopause, but a year ago she was told it was Alzheimer’s.
“It’s something I might have thought I’d get at 80,” she told the paper.
“But I was still only 61 years old.
“I felt more angry than anything else because this disease has already impacted my life in so many ways; my poor mum was crippled with it, then my dad, my grandparents, my uncle. It just keeps coming back for us.”
The NHS says Alzheimer's disease "is the most common cause of dementia in the UK".
"Dementia is the name for a group of symptoms associated with an ongoing decline of brain functioning," it says on its website.
"It can affect memory, thinking skills and other mental abilities."
Watch: Derek Draper watches as wife Kate Garraway collects MBE from William