What exactly did Jane Fonda do during Vietnam War that was consider treason?

In the middle of the war,,,she went to Hanoi, met with N. Vietnamese political and military leaders, sat on a N. Vietnamese anti aircraft gun and oohed and ahhed about how cool it was and how wrong we were to bomb the poor N. Vietnamese forces and how she didn't blame them for shooting down our planes and taking our airmen hostage. She made no mention to them about humane treatment of P.O.W.s or maybe trying to end the war. She couldn't have done any worse if she had gotten on her knees and sucked off each and every one of them. She should have been arrested as soon as she returned to the U.S.