I think its a good thing that you're asking instead of just assuming that its stupid or a fad, like I've seen before. In the beginning of your aricle, you said that you will gladly refer to a person by their chosen pronouns, so just long as they just let you know. Since we can't always tell, I think the world is just coming to understand that it seems more inclusive if we just let people know our pronouns right from the beginning. No awkward wodnering if we will accidentlly use the worng pronouns from someone, and it opens the door for trans and non-binary people to feel comfortable letting people know, instead of feeling like they are being pushy for telling people their pronouns. Your frien's email probably just has a signature that is attacehd to the end of every email, and she probably just set it to say sheher. Her workplace may be one where people all do that, or maybe one of her kids or friends use less conventional pronouns and she is being an ally. I feel like, since it doesn't hurt anything, and we are trying to be a more inclusive world for everyone, its a good thing, even if it takes some getting used to for some.