A jury also heard Senator Cash did not know about the rape accusation until two years after it had allegedly occurred.
Senator Cash has given evidence in the ACT Supreme Court trial of former Liberal Party staffer Bruce Lehrmann.
Lehrmann has pleaded not guilty to sexual intercourse without consent.
Ms Higgins worked for Senator Cash when she was employment and skills minister following the 2019 federal election.
The court has previously heard Ms Higgins talked to Senator Cash about the alleged assault several times during her employment.
But appearing via video link on Monday, Senator Cash said although she was told there had been a security breach in a ministerial office, she was not told about the alleged sexual assault.
She said Ms Higgins disclosed she and Lehrmann had entered then defence industry minister Linda Reynolds' office - for whom they both worked - after a night out drinking.
She said Ms Higgins had told her she had fallen asleep in the office.
Senator Cash said she did not recall talking to Senator Reynolds about the breach.
Asked by prosecutor Shane Drumgold if an alleged assault between ministerial staffers would be "politically embarrassing", Senator Cash said "absolutely not".
She said she did not understand the political connection, but an assault allegation would need to be addressed.
When Lehrmann's defence lawyer Steven Whybrow suggested it would be "political suicide" for a government to try and cover up a sexual assault allegation, Senator Cash agreed.
"Hence my confusion with the previous line of questioning," she said.
Senator Cash's former chief of staff Daniel Try told the court following a media inquiry about the security breach Senator Reynolds called him directly.
He said Senator Reynolds did not disclose many details about the "incident" but told him "it wasn't Brittany's fault".
In a meeting with Ms Higgins about the media inquiry, Mr Try said she did not mention the alleged assault.
He said Ms Higgins indicated the matter had been taken care of at the time and she didn't want it to go any further.
Mr Try said when Ms Higgins resigned in 2021 it was completely unexpected.
Meanwhile, Queensland MP Sam O'Connor, a friend of Ms Higgins, said she told him about the alleged assault in April 2019.
He said she described it to him as a "super f***ed up thing that had happened" and asked if he had heard anything about her.
Mr O'Connor said Ms Higgins was worried about the alleged assault becoming public and that it would define her.
She has previously told the court she felt pressured not to pursue a police complaint because of the potential implications for the Liberal Party at the federal election.
But Senator Cash said when she learned about the alleged assault in 2021 she told Ms Higgins she would be supported "every step of the way".
Senator Reynolds is expected to give evidence in the trial this week before closing arguments begin.
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