I came out to a friend of mine that I've known since elementary school today, and her reaction couldn't have been better. When I mentioned my sexuality to her she said she was happy for me, and when I mentioned that I might not be quite as female as we had thought and explained that I think I might be genderfluid, she was understanding. I told her I was still questioning it, and she said "Okay, that's fine. I mean, we all are a bit masculine and feminine inside and if you feel more like one at one point and more like the other at other points then go for it!" which was a huge relief compared to "What?! You're definitely a female!" like that was going to "change" me. So moral of it: don't be too afraid to tell your friends things!
So glad it went well for you! Your friend seems like a really great person. It's always nice when people react positively to something like that.