My Supervisor has told me that I am not meeting the expectations of my role, but doesn't really give me specific criteria about the expectations I am not meeting. I am getting the work done, she just doesn't seem to like the way I do things. I am an engin

I am a male engineer, 49 years old working for a Beverage Manufacturer in Cincinnati, OH. My Female Boss is trying to get rid of me so that she can hire a friend that she worked with at her previous place of employment. She is fabricating performance issues and constantly wants to meet with me to review status. It's become obvious that she does not like my work style and wants me gone. This morning she called me in and basically told me that she was going to have to let me go, that she was surprised I hadn't left on my own and if I wasn't looking I should be. I wasn't let go though, I am thoroughly confused. I know that she wants to hire a friend and former coworker. I belive she is fabricating issues on me so that she can push me out and hire her friend. She started the process to hire her friend some time ago, but HR has told her that she must wait until closer to the date that person can actually start. The person she wants to hire is being let go from their current employer with a severance package so she is waiting so they can take advantage of that, and then hire on here. They are friends and worked together for many years at her previous place of employment. Is this legal? Can she make things so uncomfortable for me that I feel forced to leave? I need this job. I have a family to support.