My manager despises me

I do not know how it happened but I am getting older physically - not in spirit. I have had a great career but recently have taken a job where my manager appears to hate me and from the first two weeks of the job has implied that I am unable to multitask and cannot "grasp the material." She also accuses me of being away from my desk when I am working like a dog and once accused me of not being online and I had to send her a screenshot proving I was on the phone queue. She then said, UMM HUMMM. Not believing the camera! I have a southern accent with a drawl and I realize and can make a one syllable word into three. I have not worked outside my state in years but am now on a national team, remotely, and we know each other by voice. It is a cliche that a southern accent makes one appear stupid and a Northern accept makes one appear smart. She lets me know in many ways as do her two assistants, that she thinks I am an idiot. I keep thinking when she gets to see that I am a dedicated hard worker and gets to know me and my character it will be okay.....Not happening. This job is different for me in that it is Telehealth work and speed is the main component. Everything is timed from the phone calls to after call work, ect. I did not know until hired that you have to go very fast and all work is recorded and timed. I am in 50 something and cannot compete with millennials for speed though I can type fast. . I need this job and have been afraid of getting fired from the first two weeks. I have worked so hard to do well..my productivity scores were at the top of the metric but she failed me anyway. She seems to be in a bad mood on Friday's and will out of the blue contact me in anger about something. For example, on this call queue we have back to back calls and only a 30 min lunch and two scheduled 15 minute breaks. There are multiple computer programs to learn plus insurance benefits, state requirements, and rules, rules, rules. I was on a call with one of our doctors about a patient and we were concerned and discussing a care plan. He had me took up info on the internet and I had multiple screens open. I was really listening to what he was telling me. She starts emailing me, calling my cell phone and everything because on our ongoing chat, it had been 7 minutes since she had pinged me and that it was UNACCEPTABLE to not respond to her for 7 minutes. She had not texted me on a chat in weeks and I had just not realized it. She is yelling at me over the chat and emailing as I am apologizing and trying to talk with the doctor. When my call with the doctor ended she was telling me I had been off the phone queue tooo long and to hurry hurry. I had to write the note and my hands were shaking and she was telling me to hurry and typing "what is taking so long, it is a short note" and I kept messing up due to the stress. She does this all the time andstays on me about speed of typing etc. and I get so stressed that I cannot do well. There is a lot of information to learn on this job and when I have asked for help - we have to request time to study workflow own or get another to help ; she says things like "I will get you help AGAIN" or yes "we will take up more staff time trying to help you again." I know from the other new CA's that are asking for help but their managers are supportive. The stress level for now 6 months has taken an effect on me. Then she wrote me up and when viewing it on the HR work site a I saw she had done a performance eval that I was not notified about. On this eval she failed me even though my scores and statistics had me at the highest level for one metric and average or above average on others. After my scores were noted on the eval as meeting the metric or aloe the metric s she would say it meets the metric BUT she is not getting it, she is working through her breaks to keep up, or she "suspects" I am ......accusation, accusation.. ( exAMPLE "working through hours ter to change the statistics".....always thinking I am dishonest which again started at the beginning with no c cause. Beksides being stupid she has accused me of not being at my desk during work time and of other dishonest acts. All keystrokes arShe has also accused me of asking a manger if I could take off without pay each month to get a hairdo (reference to south...big hair). She loses her temper and puts barriers in my way to stop me from having the same learning opportunities as the other CA's. I do not know what to do. I cannot take the stress and I am intimidated by her. I need this job. She has now told me if I make one more mistake until the end of the year I could be terminated. I do not know what to do. Any advice? Am I being a whiny baby or is my fear and anxiety real. Is this discrimination of age and culture?