Liberal Senator Linda Reynolds is involved in defamation cases against former staffer Brittany Higgins and her partner David Sharaz.

Failed mediation talks in the WA Supreme Court have led the parties towards a trial.

Court rulings have confirmed Higgins' rape allegation in Reynolds' office.

Sharaz is facing financial difficulties and has opted out of the mediation talks.

Reynolds is suing over alleged defamatory social media posts that she claims damaged her reputation.

The allegations include accusations of pressuring Higgins and hypocrisy in women's advocacy.

The case also involves a trust set up by Higgins to protect compensation money.

A separate case concerning the $2.4m settlement paid to Higgins by the Commonwealth is scheduled for Wednesday.