I would say, if a girl was telling you she had paranormal power and could fly like a bird, you've picked an excellent context to drop the word "wacky." Wacky is a rather informal term, and it means zany. NOAD defines it as "funny or amusing in a slightly odd or peculiar way."
You gave me a wacky move, isn't it?
That said, the sentence construct you given doesn't quite feel natural. First of all, the statement in the first of the sentence should agree more with the question in the second half. So, it would probably be better to say:
You gave me a wacky move, didn't you?
That's a wacky move, isn't it?
Also, people may "bust a move", or "show a move," but we generally don't "give a move." So, when she was flapping her arms, you might have said one of these:
You look wacky doing that – you know that, right?
That looks wacky – you, trying to fly.
Do you have any idea how wacky that looks?
I didn't realize you were so wacky.
I think that, in the context you mention, any of those would be interpreted as good-natured kidding around. (I also think that what you said would be interpreted the same way, even if the English could have used a slight adjustment.)
Lastly, make sure you stay on her good side – just in case she really does have paranormal powers.