Hmmmm - personally, I would have to respect my daughter's wishes. I feel like I'm being selfish with the time I spend on the computer already...if it really bothered her, I'd feel I owed her that. (just my 2 cents.:)
She's obviously old enough to be aware of what you're writing and what she's asking. If she has asked you to respect her privacy, you need to do that. It's not about "the point of mommy blogging," it's about respecting our children as we would expect them to respect us and not violating their trust. I would recommend agreeing with her and then, if there's something you really want to write about, ask her on a case by case basis if it's okay and allow her the ability to do some editing. And if she says no, respect her wishes.