Immigration from AU to USA

The girl I want to bring to the US has recently immigrated from Cambodia to Australia and has married to obtain AU citizenship. The marriage there would be easy to dissolve. Do we have to wait until she receives her citizenship there before trying to bring her to the US? Can she apply for a visa to come the United States in Australia while still a Cambodian citizen awaiting her Australian citizenship? Can she just get a divorce there and come to the US so we can get married? We don't really want to wait the two years it might take for her to get the Australian citizenship. I am not really sure how the visa process works so any advice would be helpful. Thank You.