"I think he's an amazing artist," she told 7.30 from her home in Berlin.
The celebrated photographer is her godfather, and from the moment she was born via caesarean section, Henson has been documenting her time in the world.
"I've known Bill my whole life," she said.
"When I was 17 he asked me if I wanted to try it out.
"The first time was in Rome, it was just an experiment."
'I was very intrigued'
Heyward is the daughter of leading publishers Michael Heyward and Penny Hueston.
Speaking publicly for the first time about her experience working with Henson, Heyward described a close and collaborative relationship.
"The light of the hotel where we were staying was amazing, so we just had a session," she said.
"I had no idea how it would be for me to be engaged in a one-on-one process like that. So I was very intrigued."
Over five years Heyward became one of Henson's principal models, featuring in memorable and iconic sequences of images that deal with one of the photographer's great obsessions: what he calls "the floating world" of puberty and adolescence.
"It was totally an interest of mine to be part of," Heyward said.
"I'm constantly working with people to realise their work as a dancer.
"It was very much, for me, about being in my body and being inside a state that we create together."
'I don't think these images are provocative'
Henson is regarded as one of the most important photographers of our times.
But his work also sparks controversy, particularly with those who do not believe that an underage model can grant informed consent to be depicted naked.
"I was under 18 and I gave informed consent," Heyward said.
"I've certainly had a grasp of my choice-making ability … and the proposal that Bill is making I don't think is a dangerous one at all."
While many voices have been raised loudly from time to time in criticism of Henson's work, famously including the then-prime minister Kevin Rudd, one group has remained conspicuously silent: the photographer's large and loyal group of models.
They have refused to add to the clamour, until now.
"It was really stupid to be honest," Heyward said of the 2008 controversy, in which Henson's works were seized by the police from a gallery in Sydney.
"I don't think these images are provocative in that they are trying to create discomfort.
"I think they are dealing with notions of beauty that aren't new or unrecognisable anyway.
"The discomfort is, I think, about dealing with nudity."
A modelling session with Henson can last for six hours, with the photographer giving his young models hundreds of tiny directions to shift and move their eyes, faces and bodies.
According to Heyward, it creates something of a dream state.
"I'm listening and trying to follow the instructions but it produces something else, I think. It creates this ongoing state of change," she said.
Heyward considers Henson one of the great Australian artists and laughs when asked if she might allow a daughter of hers to be photographed by him.
"My daughter could do whatever she wanted! She definitely could if she wanted to — and if Bill wanted to," Heyward said.
'I believe in the pictures'
After a scarifying public debate, and the intervening years, Henson remains unapologetic about his work.
"For better or worse, I believe in the pictures," he told 7.30.
"I have a good relationship with the people I have worked with over decades.
"And I have seen nothing to make me change my mind."
Henson wants visitors to the new exhibition, a collection of recent work donated to the NGV by William Bowness, to trust their own response.
"Great art is about empathy, whether it is literature or music or photography," he said.
"It is about feeling the experience.
"You want to hang onto that: a deep empathetic response is the ultimate response you can have.
"You become the subject."
The exhibition Bill Henson opens as part of the National Gallery of Victoria's Festival of Photography on March 10.
(Alice Heyward modelled for Bill Henson over a period of five years when she was an adolescent; ABC)