Odd question grammatically, but I'll endeavour to answer it.....
There is a mountain biking thread in the Cycling forum. Some of the contributors are women (very few if any are "girls"). In a lovely minimalist way the mtbers on this forum manage to keep pretty much all discussion limited to just one thread.
Outside of the BV forum there are many women mountain biking in victoria, both socially and competitively. Try the thread linked to above (not looked at it myself) or keep a look out for rides advertised through either www.ftf.com.au
There will always be a dozen or so women at any cross country race, so just turn up and have a go. Whether you're a chick who wants to compete against them or a bloke who wants to appreciate them, you'll undoubtedly be made welcome.