Can the word "spunk" [AUS] be used to describe women as well as men?

It would seem so.

Mike asks “should I take someone?” to which Brian responds “as long as she’s a spunk mate”

Australian media blog

I would exercise caution when using this term in Australia, as it may be perceived to be misogynist, and especially in Britain, where the word 'spunk' is very widely used as a vulgar term for 'semen' or 'male ejaculate', corresponding to American words like 'jizzum', 'goober', etc.

spunk google books The following definitions and usage are from: Dalzell -The New Partridge Dictionary of Slang and Unconventional English, 2nd Edition. Routledge

The following definitions and usages suggest yes, this can be used for women, and the definition is not exclusive to Australia. In AmE, the vulgar senses of spunk are rare and are in context.

an attractive person AUS, 1978 (Dalzell 2125)

mettle, courage UK, 1774

As in:

A word forever associated in the US with actress Mary Tyler Moore; in the initial episode of The Mary Tyler Moore Show in 1970, Moore’s boss Lou Grant assesses her–“You’ve got spunk. I hate spunk!”. (Dalzell 2125)

and

But then talking to her after changed his mind, seeing this was a good-looking girl up close with a cute figure. She had spunk, too. — Elmore Leonard, Maximum Bob, p. 43, 1991 (Dalzell 2125)

and

On the first day on the job in the big smoke I had to share a teller’s box with a young lady called Kim, a real spunk and my future wife. — Paul Vautin, Turn It Up!, p. 82, 1995 (Dalzell 2125)

Australians have a tendency to almost ironically devolve to bogan idioms. I tend to use spunky to describe "sexy" inanimate objects now ("that fry pan is pretty spunky") and I haven't described a girl as spunky since grade six (aka the eighties).