I know you are hurting, and I have been there myself, (and my "friend" apparently disappeared) so I have two thoughts on this:
First: Just to play Devil's Advocate: did she really lead you on in a relationship sense, intimating that she wanted to date you, or did you just hope that would happen? Because if so, as hurt as you are, at least you know she isn't malicious, which is good, and possibly means that she does actually want your friendship.
Second: If she truly did lead you on intentionally and is now saying she wants to be friends, is that something you can handle? What if she sincerely does want friendship, are you prepared emotionally to do that? I probably wouldn't be. If you do not think you are, you should take a break from her. Conversely, it is possible that she isn't sincere in her desire to be friends at all. My ex wasn't, and I know a host of others who were in the same position. Has she made any motions to be your friend since this came down? Her actions will give you your answer.
Either way, do not rely on her words, but her actions, and do not do anything that does not feel right for you, and that you don't believe will help you be stronger and healthier in your life.
Allow yourself to feel like crap, even wallow in it for a while, you've earned it. But remember, there ia a world full of dynamic, interesting, beautiful people out there. One of them is bound to want to get to know you--so don't hide out for too long

Take Care,