I always handwaved Carol flying in space by assuming that her Binary power-up made her, IDK, turn partially into enery of something. Or that the Binary energy-corona around her was protecting her somehow.

(I suspect the real answer is that no one at Marvel really cares about the fact that there's no air in space - after all, this is the same verse that has a giant network of secret tunnels under New Orleans, where the water table is so high that a lot of people don't even have basements.)