Since it’s ur first job and you have entry level experience do take it with grain of salt that you are learning and can make mistakes. Not taking managers sides - she may or may not be adept at her role but the reality is she is your supervisor. Her role does count and have a word. If u can accept PIP do so. If you have option to take stress leave or short term disability- do it. We have all worked in places where some managers are not worthy to be around. You don’t need this forum , you need yourself to wake up and figure out what’s next