If you live close to Boston, I'd strongly recommend getting a second opinion at Dana Farber, the comprehensive cancer center there. They have an online form to request this. See
http://www.dana-farber.org/pat/becoming/second/

It would be very helpful to know why your sister's ENT told her twice she didn't need radiation and then changed his/her mind.

Should your sister decide to have radiation, you should move relatively quickly to get things in place. It often takes several weeks for the preparatory stages to be completed and a mask prepared (if she'll need that). My radiation oncologist (at Mass General) told me that it is optimal for radiation to start no later than six weeks after surgery. - Sheldon