I inherited money, but will I ever get it?

My great grandmother died about a year and a half ago and left me 10k. My grandma has control of the money. I was told that I would get it when I turned 19, which was a few months ago.
Now the new story is that, “I’ll get it when I can prove that I’m responsible”. Well that seems perfectly reasonable, Except that I am responsible! I’m not going to go blow it on drugs or something for goodness sake.
Its not that I even need it now, I just want to have access to it, and I’m worried I’ll never see it.
I am completely self sufficient, I have lived on my own since 16, I have a full time job as a receptionist at a doctors office and I also go to school. I pay my rent, my phone bill, my credit card bill and buy my own clothes and groceries. I’m certainly not a child and I don’t see how my grandma would know whether or not I’m responsible anyways as I see her about once a year…Is there anything I can do?