Well, pretty much you're both somewhat wrong, but mostly you're just wrong. On any kind of professional shoot with any kind of budget, there will be some kind of art/creative/photo director on set. You're whole notion of the photographer's "artistic license" is way off. That's just not how it works. No one hires you to do what you want for their ad campaign. They hire you to do what they want. If someone has an ad campaign, and they're dropping the money to make it happen, they could care less how you wan the models to pose or how you want the light to look, if it doesn't line up with what they want. Now, that sounds horrible, but that's not really how it plays out.
The way you're putting it is in a very egocentric, self-absorbed photographer type of way, like you're the only one who is allowed to be creative, and anyone else that has ideas clearly has worse ones than you do. In reality, photogs and AD's are meant to work together to make the outcome better than either of them could have on their own. They are an asset, not an enemy. They are representing the interests of the person with the check book, and making sure that they get what they were looking for. That doesn't mean you get no say in what happens, unless the AD is truly a witch.
The bottom line is that it is there job to look at photos and judge them. That is the only thing they do. You can't just "hand them the camera", because I bet they don't know how to use one. But they know a good photo when they see one, and they know how to look at an image and know what should be changed to improve it. I love having AD's on set, it's so much better to have another set of eyes checking things out. Ever notice how when you're the one taking the photos, it's so easy to overlook details, but when someone else is taking them or when you're reviewing you own shots later, you notice things instantly? When you're shooting, there's too much going on for your brain to also be photo editing. That's why thre is someone else there to help with that.
It's not like the AD comes on set and is like "Ok, I want the model like this, and I want this light here with a beauty dish, and this light over here with a medium softbox, and ringlight for fill, and let me frame the shot for you, and I want f/2, ok now you push the button."
It more like a back and forth of the two of you working together to to get the best shots possible. But don't be mistaken, you're there to realize their vision. You get all sort of input and creative license, as long as it lines up with what they want. It's usually more like:
AD - Ok, so we're looking for this kind of shot.
Photog - I think glamour lighting would look really good for face.
AD - Ok
Shoot some
AD - I like it, but I would like less fill, for more drama.
Photog - ok
Shoot some
Photog - I think we need a separation light on her left side
AD - OK, let's try it.
Shoot some
AD - I think I would like it more coming from the right
And so on...
Usually these thing go very well, because the fact that they hired you means that they probably like your style and think it suits what they are trying to do.
And here's the other thing, if your friend does have all this experience with art directing on photo shoots, and directing poses and making lighting calls, then why wouldn't you want her helping with that? I'm sure it will only help the images look better. Or do you just not want to share any of the credit and want to be the sole source of creativity and artistic vision?