Oh my goodness. Your mother is a disaster. I feel so sorry for you. Are there no siblings, or what about your father? I'm sure if you knew of an escape you'd have mentioned it.
The bottom line is this - your mother is toxic to you. You are not at fault here, your mother is an uncaring and abusive individual who has unresolved issues in her own life. I have no idea what propels a woman to take their own personal anger out on their emerging daughter in such a way. In some respects my mother did the same thing as well. Constantly disparaging, never encouraging, and always about her and Dad.
What I did was move away at the first opportunity, which was when I was 17. Eventually, I moved overseas too and in my 20's and early 30's would go for months without speaking with them, due to the constant put-downs and critical remarks. Nothing I ever did was right, and there was always some reason why I shouldn't attempt to achieve something, whether it be personal or in my working life.
What I did was start to read some self-help emotional growth books and give myself enough courage to leave. Once I had left, my life opened up like a flower blossom. It was the best thing I could ever have done. Minimal contact back with my mother was good too.
You are going to be a great Nurse, don't let your mother take that away from you. Your mother needs help, she may or may not get it, but in the meantime, she's a big problem in your life. I think you need to nurture yourself, as you won't get it from her, and see if you can find some independent way of living. If you can gain an optimistic outlook (despite your current adversity) with lots of personal growth positives in it, then do so.
I'm now 46 and my relationship with my mother and father is good. But I've learned to put boundaries around myself, and every so often say each 6 months or so, I have to be a really little bit hard on them and stand up for my rights and there's a few topics at present that I outright refuse to talk to them about, because we don't agree, and I've found that if I don't agree with them, then that tends to be a bad thing, as out come the insults, the put-downs, the disaparaging etc., They have no respect for other people when they say 'no' or have a differing opinion on something. So that means I have to force the issue of 'respect it or say nothing.'
But good luck with everything, I think you'll do well. Your post is focussed on your mother's behaviour, rather than showing a lot of loss of your own personal self-esteem, but the sooner you can get out from the toxicity that is your mother, the better.