When she twitches her wings, is she holding them away from her body?
She may be trying to cool off. What is the air temp when she twitches? It may be too hot for her to do much more than lay around and some birds stop laying when it gets hot. (80s and above depending on what your birds are used to)
Mine spent last summer laying in the shade, napping and 'fanning' themselves (kind of like twitching their wings - kind of like a flutter) when it was too hot for them.They would keep their wings out away from their bodies some, too. I would spray them down with the hose (on mist) and put fresh cool water in their wading pool. I kept the pool in the shade.
Keep her pool in the shade, keep the water cool, and maybe spray mist her during the hottest part of the day. If you can. freeze some soda bottles of water and drop them in the pool to help keep it cool. You can wash them off, and refreeze them daily. If it grosses you out too much to put duck pool bottles in your freezer, put them in a clean trash bag after you wash them and before you put them in to freeze.
If heat is not your problem, let us know.
Can you post a video? Maybe someone can look at it and give you a definitive answer (and hopefully put your mind at ease).