^I've imagined it similarly. After all, she doesn't "breathe" the water through her nose or mouth, but through it circulating across her gill crests. So it's not analogous to a human's spacesuit helmet where you need a volume of air around the head so you can breathe freely. The crests are where you need enough open space within the suit to allow circulation, which is why I described the suit's gill vanes as rigid-walled.