I completely understand your thought process with all of these. I have my first "boyfriend" since my divorce three years ago. I'm 46.
I call him my BF and he calls me his GF and it works for me. For me, after two divorces, it's a reminder that we are NOT married. For me, it's fun. It feels youthful for me again.
Like you, I do not want to be put in a box. At the same time, my way of fighting the box is to remind myself that I am this cute man's girlfriend and I don't give two shits what other people think that means. I know what it means to ME.
Keep rocking it, Sarah.