You could start here. http://www.snopes.com/military/fonda.asp

your first question shouldn't be "Are her actions in line with the definition of treason?", but rather "did she really do this?", or "are there other sources to back up this claim", and only if the answer to those questions is "yes" should you go on to ask about treason. But the answer to those questions is "no": http://www.snopes.com/military/fonda.asp