"Mr President my door will always be open. Congrats on behalf of Pauline Hanson's One Nation Party of OZ," she tweeted.
Earlier this year, Hanson claimed Australia was being "swamped by Muslims" and drew widespread condemnation from politicians from all sides.
Christensen has praised Hanson in the past for speaking out against "political correctness" — another favourite cause of the Trump campaign.
"People don’t want this political correctness crap anymore. There is nothing wrong with being a patriot," he said.