Sounds like she enjoys gourmet/different types of foods. Rare for a teenager! Jiko seems to get good reviews but it might be more fun to acutally go somerwhere other than your hotel to make it seem like a real celebration. Blue Zoo is a good option. Does she have a favorite food? Maybe there is one of the nicer places that has a version of her fave.
We did not care for Crystal Palace but we went for dinner. We have two boys that are now too old for Pooh so we have not tried it for any other meal. I think for Sweet 16 CRT would be more special if you can get it. CRT would not be a bad choice for dinner either since she could get the glass slipper drink and the decor is just fit for a princess!
A nice treat might also be to book a fireworks cruise for after dinner and then try Ohanas or one of the resorts over by MK. How fun for her!!