@feha I guess I missed it if there were exceptions for barter with monsters vs humans, though given the extreme shoddiness of the skill in general I'm sure pretty much anything goes at this point.
Yeah, the massive drop in atmospheric pressure and oxygen content would be another pair of massive issues. In general, it's impossible for humans to survive at any altitude above 6km without external support due to low atmospheric pressure and oxygen content. Due to the mechanics of how breathing/lungs function, breathing itself becomes impossible. This is why many people who climb the worlds tallest mountains often use oxygen tanks near the peaks.
Extremely low atmospheric pressure (at 12km pressure is 1/5th of sea level) causes a second problem in that without it, your body immediately expands and swells, and at these elevations, causing a host of crippling physical complications, many of which are either lethal or result in permanent bodily damage.
Of course, the biggest problem of all here is the fact that all these changes happen INSTANTLY. The body can slowly adapt to many things, but going from normal temperatures/atmospheric pressures/oxygen levels to 12km levels all at once? This instant change would make everything happen in an explosive way. Your eyes and ears would burst, all the air in your lungs would be explosively ripped out like a popped balloon, and the body would instantly swell up like a soggy sponge. In short, it would be a horrific instant death scene.
So yeah, her first action of making a small direction shield is very laughable response to her predicament.