There's more than one side to a story.

Is it possible to send a letter or call my mothers therapist?

She is beyond abusive but I know she only shares one side of the story and her therapist can only comment on that.
She is the person who will walk up to a random stranger and call me a ****** and useless. She screams at me that I am not good enough for anything and why can't I be like my brother, which makes me fall into a deeper depression. She gets mad at me if I ask her to change a radio station because it is broadcasting something triggering to me. She throws my clothes out and takes things away b cause I can stop her.
She constantly tells me to "shut up. Yo know who you're talking to"
She says I owe my entire life to her because she gave birth to me. She says she won't give me rides anywhere anymore because I didn't grab her a glass of water, walk her dogs, get up the second she tells me to, etc.
she talks to her therapist and only says bad things about me, and her therapist tells her "no excuse for abuse", she whenever we get into a fight she stomps around yelling that and calls me names. She says its abuse if I so much as leave my shoes and stuff under my bed for her to see. I've gotten so depressed that I don't keep up with cleaning much, so she yells that I'm being abusive to her by not cleaning the second anything happens. If I cook, I have to be wash the dishes and pots, etc before I eat or it's more screaming.
Every time I try to do anything for myself (go to jiu jitsu, hang out with friends) she calls me selfish and neglectful of the family.
I hardly buy any food for the house because I am hardly in the house and she allowed my brother to put a lock on the fridge so I can't even open it, but she keeps yelling at me saying I neglect everyone. I would buy food if she hadn't have let my brother do that.
Then she always comes back a bit later saying that I'm too quiet and need to learn how to communicate so she can understand me better. She yells at me every time I try to talk to her and I be told her that. She denies it and says she's never do anything like that.
There's a lot more as this has been happening since this started when I was 5 and still hasn't stopped.
Is there a way to stop her or is my only option leaving?

Try to get out

I'm sorry you're having such a tough time. I think you should get out as soon as you can. I can't decide whether the letter or call to her therapist would make it better or worse. In any event, you need to leave. She's toxic. Sending big hugs.

Get out, there is no excuse for that type of behaviour.
Your other option is to ask her to go to family mediation.
I also don't know if contacting her therapist is going to make things better or worse.