'You're overreacting' or 'Relax'

Even writing about it makes my blood boil! Take it from a woman, nothing can annoy a woman more than these two phrases! This can be for one of two reasons. One is, she already knows she is overreacting (this one is more likely) and she is basically just venting to get it out. She does not want to be reminded of this flaw in her character.

And two, she really means what she's saying and doesn't appreciate you trivializing what she has to say. So seriously, just shut up and listen. If possible, and if the anger is not directed at you, try to give her a hug and show her you're there for her.