She doesn't need a "public interest" defence: as a Representative, she can't be prosecuted for anything she says in the House.
What is your support for this?
The Senators and Representatives shall receive a compensation for their services, to be ascertained by law, and paid out of the treasury of the United States. They shall in all cases, except treason, felony and breach of the peace, be privileged from arrest during their attendance at the session of their respective Houses, and in going to and returning from the same; and for any speech or debate in either House, they shall not be questioned in any other place.
[1] http://www.law.cornell.edu/constitution/articlei#section6
More seriously (I hope) that does sound like it should be sufficient protection and I'd love to see her exercise it.