The grand jury is an attempt to get something out of her which will sway a jury to decide that Assange is not a journalist and is guilty of conspiracy to commit

The grand jury is an attempt to get something out of her which will sway a jury to decide that Assange is not a journalist and is guilty of conspiracy to commit computer fraud. She's decided to not play that game. To not serve as an accomplice in the US Government's case against Assange. I don't know why you think there's nothing heroic about remaining silent under intense government intimidation. You can come up with a counterexample very trivially -- in the civil rights movement, if you had witnessed a black person going into a "whites-only" bathroom then it would've been far more courageous to refuse to act as a witness than it would be to tell the truth.