Very unusual behavior, why is she doing this?

[Ash]

My friend called me at about 10 this morning to tell me that her 09 female spider was behaving strangely. I got her into bp's in the first place so she assumed I might know better and be able to explain what's happening.

She said that she had put a live mouse in the aquarium with the snake, but every time the mouse got close, the snake would make a sort of high-pitched, quiet screaming sound, like a kettle boiling. The snake did this with the mouth open. I didn't believe her, so she put a camera on it right away and told me to go over and see. Unfortunately she didn't get film of the noise, and it didn't happen again after I arrived. She said it appeared as though the sound was happening on an inhale rather than an exhale. I also saw the snake open and close her mouth a few times. It wasn't a wide yawn like after they feed, it looked sort of like soft chewing.

Her snake has been refusing food (which I told her is normal this time of year). She also just recently changed the tank to a bigger 20G and put in slightly bigger hides.

During her last feeding two weeks ago, the snake ate the mouse half-way and then regurgitated. She resumed eating a few minutes later and nothing unusual happened again.

I checked the mouth for signs of an R.I. and it looked completely normal. There is no crackling sound when the snake breathes. The snake's environment is pristine, 89 degrees hot side, 75 on the cold side, identical hides, fresh water, and occasional misting. Substrate is white paper towels, changed weekly. Has anybody else seen/heard about this? What's going on?