Also possible she may have a little bit of suck shed in her nose causing the "whistle" on the exhale - we had a Carpet Python giving us a whistle when we first got her, it went away on its own (no other signs of RI). Especially if there's some other shed stuck on her, that's what I'd assume first - but do keep an eye out for RI, because if it IS that, you definitely want to catch it sooner than later!