Twitter can and often does take down individual tweets, rather than suspend entire accounts. A person familiar with Ms. McGowan’s account said her account had been frozen partly because of timing: The key decision makers at Twitter, based in San Francisco, were out of the office when the account was locked overnight. When the workday started, Twitter’s executives decided to lift the 12-hour freeze several hours early.

Ms. McGowan reached a $100,000 settlement with Mr. Weinstein in 1997 after a hotel room incident at the Sundance Film Festival, and in recent days has been vocal in her support of women who have stepped forward to reveal that the producer sexually harassed them or worse.

On Tuesday, after the actor Ben Affleck tweeted that the allegations against Mr. Weinstein “made him sick,” Ms. McGowan called him a liar, saying he had long been aware of what Mr. Weinstein had done. She has also attacked Hollywood players who failed to criticize Mr. Weinstein, writing in a tweet, “You all knew.”

Many Twitter users expressed outrage over the locking of Ms. McGowan’s account. The actress Jessica Chastain asked for clarification on which rules Ms. McGowan had violated, adding, “Asking for multiple victims of sexual violence.”