If she's studying it, and your being yourself around her and not hiding who you are, Its likely she already knows and is waiting for you to be comfortable enough to tell her. Regardless, if you want your relationship to work you need to tell her so she can understand your different thinking patterns, it will save so much confusion in the long run.
The answer on how to tell her, whenever you feel the time is right, or write her a note, do it in text, maybe show her rather than tell her, I wished my ex had just taken the time to explain to me, things like, why he was giving me a stuffed animal, instead of a hug, It would of make life so much easier for both of us.