She's never showed any other concerning symptoms like the ones you described. I checked on her today and she seemed perfectly fine -- contently coiled under her paper towel roll, very bright, and no whistling to speak of. I'm probably overreacting a little, but I'd rather be safe than sorry.
A bit of late-night browsing through some of the older threads here uncovered this thread on carpet python noises. Apparently some past keepers have experienced similar whistling with their carpets. This response from Michael Pennell (!) was quite enlightening:
... so, I think you may be right in her just being more "talkative." Didn't know that was a thing with Papuans.