Well, at least she bought you the clothes- She's not entirely opposed to it. These things do take time, I'm waiting until I reach legal age to do any medical transitioning (My parents would likely put it off as long as they could, making sure I'm sure- Which at this point isn't too bad, I have only a couple of years left). The best thing is understanding in these cases- See where she's coming from and hopefully she'll do the same for you. Meanwhile, I've found that unless you are in a very conservative area, people will be accepting. Especially young people.
Everything will take some time, which is painful to hear- What does help is finding someone to talk to, counseling, and coming out completely in a safe and non-judgmental environment. What ever her standing is on the issue, she probably won't reject the idea of getting a counselor. It was helpful for me to have someone somewhat unbiased about my life and just to talk to- And a diagnosis is one of the first steps for medical and legal transition.