Purple, I think you should tell her sooner than later. She has indicated she will be supportive and I'm sure only said you don't need to rush to keep the pressure off of you, that's all. I think when we have these feelings but are unable to talk about them, they are intensified so much that it almost feels unbearable. Once you get your feelings out in the open with her, you may feel relieved and your feelings may even be deflated.
I hope this helps. Good luck.