and yet her sentence was commuted where Snowden remains a fugitive.

There aren't really any eggshells to walk on unless you're inventing them (and the person you replied to was not impolite about the correction). Chelsea Manning identifies as a woman. This isn't something that happens overnight; it's impossible for you or I or the great-grandparent to know when Manning decided to come out to family, friends, that sort of thing. As such, it's incumbent upon us to use the most currently, and thus least likely to inadvertently offend, pronoun and referents. (This is also why it is poor form to use a trans person's pre-transition name when referring to them in the past tense. In my experience, if a trans person would rather be described using that prior name or prior pronouns for his or her prior self, he or she will let you know.)