Because I'm obsessed with seeing Australian & NZ models on Vogue covers, I actually counted & I think she's only had 5 Vogue covers:
Vogue Australia - Oct 1989
Vogue Australia - Mar 1995
Vogue Australia - Nov 1997
Vogue Australia - Sep 1999
Vogue UK - Oct 2004
It's surprising to me that she wasn't on Vogue Australia covers more in the 80s but then she was definitely an Elle girl with loads of covers and of course, being married to "Mr Elle", Gilles Bensimon himself, so perhaps thats why!
Not surprisingly, the Aussie with the most Vogue covers is Gemma Ward with 24 (when I stopped counting - imagine if she never retired!); Abbey Lee Kershaw & Sarah Murdoch (nee O'Hare) with 12 each; Catherine McNeil has 8; singer Kylie Minogue has 7 Vogue covers; Miranda Kerr has 5; Julia Nobis has 3. And fellow Antipodeans (New Zealander's) Kylie Bax has 11 & Rachel Hunter has 3!
Others like Nicole Trufino, Kristy Hinze & Kate Fischer have 3 each (& Jenny Hayman with 2) but they were all for Vogue Australia.