So a while ago my (younger) sister and I were talking about who we liked and I said the name of a girl, she was a little surprised but took it in stride... I thought this was cool and forgot about it really, until we were visiting our grandparents and had to share a bedroom, the topic came up and I told her she could ask me yes or no questions, the first one was "does she have brown hair?" It made me so happy, up until that point I wasn't really sure what she thought or my being gay but now I know that she doesn't think it's just a phase or stupid or anything!
That must be such a relief. You're right, your sister is so cool! It's good that you can talk to her about these sort of things.
It's stories like yours that can warm even a heart of stone. You have a cool sister. Now if you'll excuse me, there is some magma I need to clean up of the floor.