It's probably best to see whether or not she knows anything about nonbinary people, and if she is accepting of them. Then try and educate her on what it means to be agender as well as whatever else, just to help her open up her mind to the concept. Keep in mind that it can be quite confusing for people to understand how one can feel like they have no gender, so be patient if you can. Finally, if things seem to turn out well, come out. Alternatively, you could just write her a letter explaining it all. This may be ideal if you feel like you may not be able to articulate your thoughts in person.
