Okay, so to start off, I've only been out to her for about a month or two, so she's bound to get it wrong sometimes. Other than that, she's been using it as a "punishment system" or something like that. She will talk to me using my dead name and then says my preferred name if I don't answer right away or give her what she wants. I usually don't fall for that, but when I do something that makes her mad or annoyed, she says something along the lines of; "don't make me say it. [deadname]." and waits for me to react. She's pretty young and I know she thinks it's funny or something, but it's starting to hurt. I've told her it really doesn't help but she just glared at me and continues doing it. Any advice?
Are your parents any help with this? Would explaining to her that doing this is really hurtful and if she continues, you will no longer do XYZ for/with her? Assuming you do things together that she enjoys. Also, a bit of silent treatment might work as I’m guessing she enjoys attention. And then when you talk to her again, explain that’s what will happen again if she can’t respect who you are and how that means using your correct pronouns and name. Good luck.
I can't really tell my parents as I haven't come out to them yet and they are slightly transphobic. I will try out what you said and see if it works. I am 99% sure it will. Thank you so much.