I think it's time to tell when you feel safe with the person, and feel a desire to share your feelings.

One thing that might help to resolve your concerns about telling is if you tell her what those concerns are! Just say, I want to open up to you about this and I'm going to, but first I want to tell you why I'm a little scared to. I think that will help set your mind at ease.

Good luck! I think it will be a good experience for you. Keep us posted, ok?