I feel your pain.
We are going through the same thing with our DD6!
It doesn't matter what the decision is, as soon as I give an opinion or suggestion the exact opposite is done. We've actually gone to giving her the opposite of what we want to happen just so that what we want actually happens. (For example clothes to wear, food to eat etc.)
On really bad days I actually refuse to answer until she tells me what she wants, then I say I want the same thing. Which she then informs me is not allowed and unfair and goes off in a huff.
It was the worse when we were on vacation. I think it had to do with her having too much time to think about all of the possible options, and outcomes of those options that she just wanted to see if someone else would choose the same thing she was choosing.
I'm sorry I have no advise, but I think it is more an age thing than anything else.
This too shall pass has become my mantra
