Yes, I've been stabbed in the back several times. You can do nothing about nor you can't preview it... She actually may not agreed with you in the beginning, just said she was ok because she thought it was a joke, a phase, or whatever, then when she realized you were serious about it, she went mad. Or it may be what Mrs Erocse says, then is just a selfish person.
I usually follow the "if you don't like it, don't look" and just ignore the horrible things that people who don't agree with me says. Even if "people" includes family, parents, friends, girfriends and such.
Hope she understands soon, or at least stop saying such things to you and let you just be-. Good luck!