I have a few ideas about "methods" to attempt on this one. Which may sound condescending, but I'm taking your word for it that you definitely should have the final say. I wouldn't normally take somebody's word about that, but an award-winning professional should definitely get the final say. It's like if Jonathan Franzen wrote a novel and then some chick with little writing skill edited it and INSISTED on the edits. That'd be no good.

So here are my ideas, and some combinations of them will be good and some work, so use your judgment. Or reject them, since you get final say. ;)

First

I have found that most people need a certain "amount" of whatever it is that they want. There are some demanding narcissistic assholes in the world, but most people mean well but just crave certain things. In this case, she craves decision making. She doesn't want to give advice. She is not craving giving advice. What she is craving is making the decision.

So give her a bizillion chances to make the final decision about *everything you can stand her making the final decision about. You want Indian food and she wants Chinese? Chinese it is! You want one car and she wants the other? Suck it up, and do what she says. Blahblah etc. You get the idea.

Then, one or both of two things will happen:

She'll have gotten her fill of decision making.

And/or

You'll have a whooooole lot of leverage about getting final say on business stuff.

Make sure to add in -- if she hasn't gotten her fill of "final say" -- "But honey, I definitely like for you to have final say about [whatever other things]. I know you're better at [whatever those things are]. So in this, it is important to me to have final say. This is the topic in life where I shine, you know? It's my "thing". I know my stuff and this is what I need. Do you think I'm not good at this?"

Ask the last question in a way that seems insecure -- not in an accusing way.

Second thing

Or just talk it out with her if she's typically reasonable. With my partners, I have a standard I follow: whoever cares more "wins". A good example would be the names my daughter's dad and I chose for our child. He cared a whole lot, but I cared more. I am a name-nerd (like I go to message boards just to talk about names, and have since I was thirteen!) and I made it very clear to me that I would find it actively disturbing if we did not give our child a name that made me very, very happy.

Third thing

I gave him options. The same way someone might do that with a picky kid. Some people just don't do well with all the options and so they need the options to be limited. So you could go, "I will do this or that. You choose which." Even if it's just two shades of blue.

With my daughter's dad, it was, "Here is the list of names I like. Eliminate the ones you can't deal with as names for your child." It was a long list of names, so give her a looooong list of similar blues. He removed names. I said which of the ones left I liked best. He removed some more. I decided which of them I liked best of which he had left. This process happened until we arrived at two left.

He loved both names, after all that rejecting my choices that he'd gotten to do.

So I "won". :) I made the final choice.

Try that. Give her a chance to reject many things. Then you make the final choice, once she feels like she made most of the choices.

Anyway, good luck!