Her going through a vent must be like putting a rubery pillow through a metal pillowcase. Weird analogy I know, but the hefty "fwomp" of her soft body squishing and re-conforming to the shape of the ventilation shaft as it passes the lip of the vent hatch feels it would be a similar feeling/effect.

(Sry if that sounded a bit weird or if i went a bit too far with the details 😅)