Liberal Senator Linda Reynolds is threatening defamation action against Brittany Higgins over a social media post by the former staffer.
Ms Higgins on Thursday said she had been contacted by the former government minister about the action.
"I've just received a concerns notice from @lindareynoldswa threatening defamation over an Instagram story," she posted on Twitter.
"I'm considering my legal options."
Ms Higgins alleged she was raped in 2019 by Bruce Lehrmann inside the ministerial office of Senator Reynolds, for whom they both worked as staffers.
Mr Lehrmann consistently denied the allegation, and his trial in the ACT Supreme Court was derailed by juror misconduct.
Prosecutors decided not to pursue further action, citing concerns of the impact it may have on Ms Higgins' mental health.
Senator Reynolds said she had been the target of "unwarranted criticism and abuse" ever since Ms Higgins went public with the allegation against Mr Lehrmann.
"Despite her repeated defamation of my character, until now I have not taken any action against her personally - even though I considered her words to breach our previous settlement agreement," the senator said in a statement.
"Yesterday, Ms Higgins made yet another defamatory post about me.
"I have had enough. I will not tolerate being defamed by her or anybody."
Senator Reynolds is also pursuing action against Ms Higgins' partner David Sharaz over five allegedly defamatory social media posts.
The matter involving Mr Sharaz was briefly heard in the Supreme Court of Western Australia on Thursday.
The court heard Mr Sharaz had not responded to communications regarding a writ issued by the court earlier this year.
Justice Marcus Solomon granted an order that Mr Sharaz be served with the writ by sending it to two email addresses and to Ms Higgins' lawyer.
Speaking outside court, Ms Reynolds' lawyer Martin Bennett said the granting of the order would require Mr Sharaz to enter an appearance and defend his conduct.
The separate notice to Ms Higgins asked her to remove the allegedly defamatory material, apologise for it and "offer to make amends", he added.
"We'll wait and see if it gets a response from Ms Higgins," Mr Bennett said.
"Her tweet today said she was considering her legal options. One of them would be to say sorry."
