To tell you this, I kind of have to spill my real name, so here it goes:

My name is Abigail. When I was younger, I was abused by my mother's side of the family and given a great load of trauma. To shorten my name, they called me Abbey.
Now, I live with my dad, step mom (who I call mom), and 7-month-old baby brother.
This morning I told my step mom that previously, little kids who couldn't pronounce my name had just called me Abbey until they could pronounce Abigail. I then asked her if my little brother, when he started talking more, would NOT call me Abbey.
My step mom then blew up at me because of what I said and refused to let me talk to my little brother afterward.
She said I "royalty ticked her off" because I refused to let my little brother, who's only word he's said thus far is "muma" and "ma", not make it easier to say my name.
One thing my mom must not understand is that when I remember my past trauma, the memories roll around it my head for hours. I have to acknowledge the trauma. Remember it, feel it, think about it, and share it.
It's horrible to relive it, so if my little brother is (in the future) going to be calling me Abbey ALL THE TIME and having me relive this every few minutes, what do I do?
PLEASE HELP GIVE ANY ADVICE SAY ANYTHING!!!!!!!!!!

It sounds like your step mom is not understanding the emotional impact that hearing your nickname has on you. It is understandable that you would want to protect yourself from having to relive the trauma you experienced in the past. It is important to communicate to your step mom why you don't want your little brother to call you Abbey. Explain to her that hearing your nickname triggers memories of the trauma you experienced and that it is difficult for you to cope with. Ask her to help you find a way to protect yourself from having to relive the trauma.

It may also be helpful to talk to a therapist or counselor about your experiences and how to cope with the trauma. A therapist can help you find healthy ways to manage your emotions and help you find ways to protect yourself from having to relive the trauma.

Talking to her won't work because she calls me Abbey when I'm in trouble. She knows the impact is has on me and she does it on purpose.