The same thing happened to be 'cept with a boy. He is also a huge Zelda fan, and I had liked him for two years. So I told him my feelings, and he had the same so we kinda went out.(Yes I know I'm fourteen, but we didn't actually like 'go out'. We just hung out at our school football games.)
So everything had been great for awhile, except my friends and I all noticed he began to get a clingy to me. Eventually, he tried to holding my hand and touching my thigh, and I realized he was sort of creepy, and I didn't really like him anymore.
So I told him that I didn't like him anymore, and he said okay and all, except I've noticed (so has my mom, dad, sister, and friends) that he constantly... stares at me. And It frankly creeps me out.
I don't talk to him anymore, and it is extremely awkward to see him at school.
Enough about me though. I think that you should ask her out. If she says no, then the fact that you've known each other for so long and are like best friends, then your friendship should be fine.
I think that if you really like her, then you should ask her, before she finds someone else, or thinks that you don't like, like her.
So I give you the Triforce piece of Courage to ask her out! You don't know until you ask!!!
Good Luck!!