If your girls best friend likes you like that and you don't like her like that and you have all ready told her yea it might have hurt but if she is a good friend then she will undersatd and come aroud.I say right now give her her space and she will soon find out that its better to have you in her live as a friend then not haveing you in her live at all.
Listen Dear One, This happens all the time. Good friends of opposite genders. Sometimes when one of the friends suffer disappointment at home, had a bad day at work, breaks up with a love interest, or what ever, they often began to see their best friend as a love interest. I would not continue to contact her. She is embarrassed, and hurt, but she will soon understand that having your friendship is better than whatever it was that caused her to want to go down another street with your friendship. When she comes back, stick to your guns about being friends, chances are, it will never happen again. Give her time. Best wishes to you.
If shes really your friend she will understand the fact that friends is all you want right now and if she doesn't maybe shes not your friend and that's okay there are always other people in the world that are willing to listen and also if you try talking to her and she won't respond try leaving your feelings about the situation by leaving her a voice mail or a heart to heart letter and send it in the mail! ANYTHING TO MAKE HER UNDERSTAND THAT YOU ARE NOT READY!
Don't go out with her it's a breakup and heartache to your girl and she will be magerly upset