Hi OP
I hope you don't mind me asking, but are you sure hormone delaying medication is necessary at 8? She's not actually outside of the normal range for puberty symptoms.
You mention that the she is the only black girl in school and I wonder if this might make her development seem more extreme in comparison to her peers.
At 9 is was in a C cup bra and 10 I had started my periods. Although this was early, I wasn't alone amongst my black friends.
It is medically accepted that black girls start their periods earlier, and the physical contrast amongst different races is sometimes quite striking within that 8-12 age period.
I do wonder if the lack of diversity in her school makes this stand out more?
And again, if your healthcare providers are not used to seeing many black people, this may be another one of those things treated with a one brush fits all approach. Incorrectly.
Perhaps do some asking and looking around. Hormone therapy seems a lot for such a young girl to go through.
Back to the actual post. Yes, I would allow her to do whatever made her more comfortable as long as it didn't damage her. Shaving will be fine. I spent most of my early years and teens in 2 minimising bras!
It's important to facilitate as much as you can of what she asks so she keeps open communication with you, My mum pretended I didn't have the body of a 20 year old at 12, and I spent a lot of those years dealing with male attention that I didn't know how to navigate. I also had a lot of female attention which assumed I should know certain things or dress in certain (modest) way because I was 21 rather than 11!
I hope she find comfort in herself OP and well done for listening to her.