I agree it sound like an RI too. Snakes will go off feed with RIs as well.
Speaking of RIs, I just took in my new big female to the vet today for a very mild case. Me and my bf monitored her for a week straight (everyday we checked inside her mouth - saw bubbles and mucus which never improved even after bumping her temps up) so I got her in and she's going to be on a round of Baytril via injections/shots. I would check inside her mouth and see if you can see bubbles or mucus and go from there (great vid: http://www.youtube.com/watch?v=XK0Uvln4lY0). A vet visit is always recommended as RIs can go downhill very fast.
On a other note: she could have some stuck shed which is making her make sounds, check her nostrils.