Am I too "young"?

I know who I am. I started using different pronouns when I was in year 6 (11 years old) and I have proof of that because I had a gacha YouTube channel lol. My earliest irl memory was giving a note to my friend who was muslim and had different beliefs than me. We were best friends, and i was afraid to tell her. When i did, she walked after me outside our class and hugged me. Even if I didn't start putting in the effort to look more masculine until year 8, I still didn't feel comfortable with my legal name or pronouns. I have told my mum multiple times that I am transgender. For reference, I'm turning 16 in April. I want to start medically transitioning (testosterone) as that's the age you can in Australia with parental consent. I've tried to get her permission to change my name on the school system, I use my name at work, yet she still insists I might change my mind by the time I'm an adult. Like I'm literally graduating next year. I'm over here upset because I feel like I'm coming to terms that she's just not going to accept me ever. I also feel like I'm letting everyone down. I don't know, it's just a weird feeling that if I really give in to who I know I am then it will disappoint some of my family. My pop always talks about how I'm going to get a growth spurt and be tall and skinny and all that, talks about stuff we will do when I'm an adult.. is he going to like me if I transition??? I don't know. This is lowkey tearing me apart. Please give thoughts cause I really don't know what to do and I'm really really set on trying to start testosterone when I can in the future.