In interviews with CNN and Reuters, Grisham said she was compiling a group that so far includes about 15 former Trump White House staff. They include Olivia Troye, a former national security aide to former Vice President Mike Pence, and Anthony Scaramucci, a New York businessman who had a brief stint as Trump's communications director, she said.
What influence the group could have is unclear. Trump is supporting a handpicked group of Republican loyalists for seats in the November 2022 congressional elections and pondering another run for the White House in 2024.
More than half of Republicans believe the election was "stolen" from Trump, despite the lack of any evidence, Reuters polling shows.
"I can say that next week, a group of former Trump staff are going to come together, administration officials are going to come together, and we're going to talk about how we can formally do some things to try and stop him, and also the extremism, that kind of violence and rhetoric that has been talked about and continues to divide our country," Grisham told CNN.
Grisham testified on Wednesday night before the congressional committee investigating the Jan 6 attack on the US Capitol. She did not elaborate on her testimony.
Grisham resigned as Melania Trump's chief of staff on the night of Jan 6, 2021, after Trump's refusal to work to halt the protesters' attack on the Capitol that day. She had also been White House press secretary for a year.
Even if no criminal charges are brought against Trump, Grisham said, the committee "is going to show you know, irrefutable proof that he was behind this."
Grisham released a tell-all book last year that criticised Trump and his entourage, "I'll Take Your Questions Now: What I Saw at the Trump White House."