Well. As some of you are probably aware, I've been coming to terms about possibly being trans. I told my sort-of-sister (We're not actually related, but I've known her most of my life and would trust her with my life) Krystal, and...Well, she didn't take it so well. Not to the point of her outright disliking me, but it was clear she wasn't comfortable with it. It'd be one thing if it was one of my more distant friends, like Edwin. But Krystal? It's been hard to imagine even living outside of a few miles of her (She's moving across the country shortly). And now I think I might have alienated her, or at least started on the path to it.
EDIT: As an aside, should also be noted that those aren't their actual names.
*hugs*
Be patient. This is very new to her- much more than to you.
Maybe she just needs to think it through a bit. Give her some space and time, she could probably come around.
To add to what Truean and Caroline were saying, do what you can to test the water about gender stuff in a general sense with people who are close to you first. For one, you want to stay safe, and have as smooth a transitioning experience as possible; having major parts of your support network uprooted very suddenly is Really Bad News. Also, coming out as a different gender can be a lot for some people you know to process, and you want to be both honest and gentle with these people.
I started doing water-testing questions with friends and relatives, asking their thoughts on gender and sex as separate spectra or talking about trans-folks in general, after an experience I'd had with an ex. I took it for a safe space, and a topic they'd be comfortable and familiar with, since we'd talked about my not really fitting a traditional gender role before we'd even started dating. After the transness thing started to click for me, I kinda launched straight into talking about how I'd been questioning my gender identity, wanted to try some things out to explore the idea, and about the possibility that I might want to transition some day. I think they wanted to be supportive, but it was obviously a topic that caused them stress; one day I'd get heartfelt reassurance and support, and the next day it'd explode into an argument or an anxiety episode. It seemed like they were repressing a lot of feelings about it, and a common assumption that I had to argue against was that I'd suddenly become a completely different person. It was a hard discussion all around, I think.
So yeah... especially with more traditionally-minded people, or those who haven't had existing relationships (ie. friends, relatives, etc.) with people who have "changed gender" on them, try to find ways of talking about it in a general sense first, to get a feel for things, and be sensitive for how best to explain it to them in a way they'd understand. Honestly, a big part of the transitioning process as I understand it is letting your existing relationships get comfortable with who you are, reassuring them about what will and won't change about you, and helping them to rebuild their mental idea of who you are. It's also important to get a feeling for what relationships or environments are going to support you, and which are not... and sometimes this involves making tough choices, or even losing someone you thought of as a friend.
All you can do is represent yourself as honestly as you can, open the floor for questions, and give them time. As with many things, I think the majority of people can eventually come to an understanding, given enough time and honest discussion about it. And for those that won't support or understand you in it, going your separate ways is often for the best anyway.
Good luck to you, and I hope it's as smooth a process as possible.