The model - who is married to former England footballer Peter Crouch - posed for the famed photographer to mark the launch of the charity's new 'Shave or Style' fundraising campaign.
The campaign - which also features photographs of singer Nina Nesbitt and presenter Gethin Jones - hopes to encourage the public to change their own hairstyle and make a donation to the cause by presenting shots of celebrities like they've never seen them before.
Abbey, 28, said: ''When Macmillan asked what style I wanted to trial for the Rankin Shave or Style shoot, I knew I wanted to try something really different that people wouldn't immediately recognise as 'me'.
''I've always had long, blonde hair so in the end I went for a short punky look! It was so much fun to experiment and trial a new style for the day.''
Rankin, whose real name is John Rankin Waddell, explained: ''The Shave or Style shoot for Macmillan really gave me the chance to challenge what people expect from Abbey, Nina and Gethin. It was great fun but it's important to remember that at the end of the shoot, all three left as they arrived, yet for those affected by cancer - long standing changes to appearance such as hair loss are a day to day reality.
''Shave or Style encourages people to try something different in order to recognise that changes to your appearance affect not only how you look, but also how you feel.''
To take part in the campaign and stand proudly alongside those affected by cancer facing physical changes, Macmillan is asking people to either brave a shave, or trial a style, and share photos of their new do on social media.
Participants are also asked to text STYLE to 70550 to give £3 to the cause.
'The Now Now' will be released on June 29th, and two new teaser tracks have appeared - 'Humility' and 'Lake Zurich'.