First and foremost, remember she is your daughter, she always will be no matter what.
I would understand your reaction (in a way) but I would suggest telling her you still love her no matter what and will respect her life choice, whateve that may be. It may be a phase, maybe, but if it's not, I suggest you talk to her about it and how she feels exactly on the whole thing, what she thinks of, etc. Also, your daugther told you (at such a young age, no less) what she felt and was being completely honest with you. It means she loves you and wants you to acknowledge that part of her which she is feeling.
There really is not specific way to go through it, but honesty and communication is the best thing to do, and know that she is still your daughter no matter what.