

It’s important to remember the word ‘ideal’ that dictates the conditions needed. The gas cannot be mixing with an ‘external’ source, gaining or losing energy to it’s surroundings beyond the changes being specifically examined, is not subject to any forces or conditions not considered, and so on…
You’re literally asking ‘at what point are perfect conditions, impossible to every truly achieve, implausible?’. The answer to that: as soon as any factor cannot be simply ignored for the sake of simplifying the math.
Nah, her nose definitely moved. She does it twice in this clip and her nose moves both times. https://youtu.be/115T9BInGIc?t=198
Edit: To be clear I agree she’s using her upper lip but it ‘does’ cause the nostrils to wobble side to side.