OP here.
She has coyly said once before when someone else asked that it is a well known cook, and she changed the subject. I am a close friend however, so thought she would share if it is a widely known author and public recipe. Personally I think it is rude given this, but that could be the cupcake withdrawal talking 
This email to her facebook email account is my first ever request. I am cheekily using the phrase grinch because she will not acknowledge my request at all but is happy to comment on other emails and facebook entries. She is flat out ignoring the existence of my email and this has me astounded. A simple no would be fine. Disappointing, but at least an answer.
The complete lack of a response had me wondering if I had committed some unpardonable sin by even asking. And it is not like I have pestered her 
Not giving you the recipe, close friend or not, is not rude. It
may have been rude for her to not even respond to your e-mail but thats it. I understand that you're put off, but that doesn't make your friend automatically rude. I have a cookie recipe that I would never, under penalty of death even, tell another single soul. I got it from my father, but he says he got it from a specific older edition famous cookbook. I wouldn't give it to my in-laws, my friends, or a perfect stranger on the other side of the world.
ETA: I singled out my in-laws because my family already has the recipe through my father