You are not rude for asking. But, considering this is facebook, and all the reasons for a legitimate non-response, I'm not willing to declare your friend rude either. This (the overall thread, not just the OP) seems like much ado about nothing to me at this point. YMMV, IMHO, so forth, and so forth.
I agree, neither one is really in the rude here. Etiquette doesn't say we have to directly answer questions. Isn't that what bean dipping is all about? The Cupcake Master has made comments on the OP's wall, etc. So it doesn't seem like she's giving her the silent treatment. If she was, she wouldn't say anything. For all we know, maybe the refusal to give a recipe has been a touchy topic in the past so she's just sidestepping it. Personally, I would use the 2nd request where the OP says it's ok if she prefers not to give it to say something like "thanks for understanding" but there could be reasons or preferences why she's not doing so. That makes her different from some of us, but not rude.
I have a relative who has no respect for the boundaries of others. One example is her friend we'll call Debbie. Debbie suffers from depression. This relative organized Project Debbie where she emailed a group of about 20 people, most of whom didn't know Debbie very well and informed them Debbie's depression was getting worse. And even though some of it was her own doing (believe me, I can't believe she said something so stupid either), we should all write cards to Debbie to cheer her up. Then gave Debbie's mailing addressed to the entire list, most of whom didn't have it. It was wrong on soooo many different levels. This relative recently joined Facebook. I ignored her friend request and blocked her. Due to her disrespect for boundaries, I don't want her to have access to my profile or to be able to write on my wall. She once attended a work related function with me when a professional organization held a conference in a city where another of our relatives lives. When I greeted a male former co-worker and chatted with him a bit, she told my boss "looks like familyfun's getting lucky tonight". There is no way in the world she's getting access to my wall. If I call her on her behavior she gets offended and refuses to speak to me. Which makes it awkward for other relatives. So whenever she's brought up Facebook, I bean dip.
Now I'm not saying the OP did anything wrong or would react unreasonably to being told no because there's nothing here to indicate that. But for whatever reason, the friend doesn't feel comfortable with a direct no. Given the friend's been a good one in other ways such as making the cookies and bringing them by with newborn items when the OP's 2nd child was born, I'd let it go and focus on the good parts of the friendship. We all have our little quirks. I would chalk this up to quirk rather than rudeness or snub.