that's why you should pay attention to the music. It is synchronised with the rotation of plates for most of the bosses
Not tryna be Captain Obvious here, but unless you're on Impossible mode, you can just dodge the falling cup attack. Otherwise, when the plate rotates just when she is about to attack, you gotta DASH with the cup yourself and anticipate the position of it after the rotation. I guess it would be really difficult for the average player but it is doable.