Ms. Fields said that she considered several requests from other conservative outlets, but said she was ready for a change after months of fallout from an altercation with Mr. Trump’s campaign manager, Corey Lewandowski.

Ms. Fields accused Mr. Lewandowski of grabbing her arm and shoving her when she tried to ask Mr. Trump a question at a campaign rally in Florida on March 8. Mr. Lewandowski was charged with battery, though prosecutors in Palm Beach County decided not pursue a case against him. Though the police said that her account of what happened reflected what was recorded on security cameras, both the Trump campaign and Ms. Fields’s former employers at Breitbart initially questioned Ms. Fields’s credibility.

“How do you know those bruises weren’t there before?” Mr. Trump asked after Ms. Fields shared a photo of her arm that showed where she was grabbed. Mr. Trump’s criticism came during a period of heightened scrutiny on his campaign rallies, which were marked by violent scuffles between protesters and Mr. Trump’s supporters.

Ms. Fields called the following weeks a “dark time,” and said that in addition to leaving her job at Breitbart, she was forced to move to a new home in Washington after her home address was made public. Both Fox News and BuzzFeed initially published Ms. Fields’s personal information without redacting it from a police report before removing the original reports.

Ms. Fields said she also lost a guest role on the Fox News show “Cashin’ In” as a result of the fallout. (Fox News disputes that and the show’s senior producer has said that he was open to Ms. Fields making future appearances.) Several other Breitbart employees left their jobs in solidarity with Ms. Fields.