In the wake of the Jan 6 Capitol riot in 2021, Mr Trump was banned from Twitter for messages the site said risked “further incitement of violence”.
The Republican presidential candidate has since formed Truth Social, which is now his preferred social media platform.
Ms Westerhout, 33, was forced to resign from the White House in 2019 after she reportedly bragged to journalists at an off-the-record dinner that she had a better relationship with Trump than his own daughters, Ivanka and Tiffany.
When asked about the dinner with reporters by the prosecution, Ms Westerhout began to cry in the witness box and spoke of her regret over a “youthful indiscretion”.
Ms Westerhout was also asked about a 2020 book she wrote titled “Off the Record: My Dream Job at the White House, How I Lost It, and What I Learned”, which describes Mr Trump in a favourable light.
“I thought it was really important to share with the American people the man I got to know,” she said through tears. “I don’t think he’s treated fairly.”