She reveals they met shortly after she turned 20 in November 2007 and spent Christmas together (Dec07) in their hometown of Perth, before heading back to New York, where Ledger passed away less than a month later.
Now Ward has told how she was struggling through a "hard time" during their relationship and sought comfort in Ledger, who was also battling personal demons.
She tells Australia's Sunday Telegraph, "I have taken a break from the media spotlight for the last few years and it was something spurred by Heath's death.
"(Heath and I) first met in New York and we were both struggling with things that I won't get into, and we bonded over that.
"I kind of met him at first and said, 'Listen my mum's living with me right now and I'm kind of going through a hard time and I'm not interested in having a serious relationship with somebody right now' and he was like, 'Let's just be there for each other through these hard times we're both going through.' And we developed a relationship and we started seeing each other."
The 23 year old insists she feels fortunate to have known Ledger, adding: "There was no one like him - and no one will ever be like him. I'm just so grateful I got to meet him and get as close as I did with him."