If you two have been friends that long she's probably weighing out the pro's and con's of how she feels, and trying to figure out if she loves you too much as a friend to risk the relationship or if she thinks you two are meant for more, so your best bet in my opinion and that's all it is, is to take a deep breath and a step back for the moment and let her ponder it over, cause if you push anyone to make a decision it usually ends badly, and you could end up losing her as a friend as well of any hope of dating her, but you made the first move and opened the door and now it's up to her to decide, so the only thing you can really do is be patient, and wait, and support her in her decision no matter which way it may go! I'm pulling for you though for whatever it's worth, and I hope no matter which way it turns out you don't alienate her like I did mine, Cause she might be thinking no for now and not no forever only time will tell! Stay positive and things tend to turn out the way they should!