If you're referring to the scene where she deliberately exits an airlock, then she actually exhaled whereas the other person with her did not and died.
(Purposely being vague to avoiding spoiling anyone on this great series)
I rewatched this moment on Prime and I remembered it correctly. While she exhales after last words slowly, she inhales sharply before pressing the button.
I remember it probably because I watch everything with subtitles on and that was written. I now watched it without to avoid being biased and it still holds.
In addition she was exposed to the vacuum about 40 seconds before using the shot.
I rewatched this moment on Prime and I remembered it correctly. While she exhales after last words slowly, she inhales sharply before pressing the button.
I remember it probably because I watch everything with subtitles on and that was written. I now watched it without to avoid being biased and it still holds.
In addition she was exposed to the vacuum about 40 seconds before using the shot.