“As someone who worked in the West Wing, it’s not surprising to me that she would have overheard these conversations and witnessed these things because she really did have that much access,” said former White House deputy press secretary Sarah Matthews, who resigned after the Jan. 6 attack.

Ms. Hutchinson has faced a wave of online attacks from Mr. Trump’s supporters and is said to have security for her own protection, according to people close to her.

“She is waking up to a different life,” said a friend who worked with Ms. Hutchinson and spoke with her after the testimony. “She’s gotten threats. She’s going to be recognized. There’s a swath of the county that’s made up her mind about her.”

Her testimony shocked some of Mr. Trump’s associates, not just because of its content, but also because of who was saying it. Ms. Hutchinson was known in the White House as somebody who was fiercely loyal to Mr. Meadows, some of the former officials said.