The degree of power shown by Galadriel in the movie is far in excess of the book: although in the book she was capable of destroying Dol Guldur (and the suggestion is that she did so single-handed), taking on Sauron one-to-one would have been beyond her capabilities.
Tolkien's Letter 246 states up-front that Gandalf was the only one who had sufficient innate power to take on Sauron, but that while Galadriel evidently felt she could, she would have needed to be augmented by the Ring in order to do so:
Of the others only Gandalf might be expected to master him – being an emissary of the Powers and a creature of the same order, an immortal spirit taking a visible physical form. In the 'Mirror of Galadriel', it appears that Galadriel conceived of herself as capable of wielding the Ring and supplanting the Dark Lord. If so, so also were the other guardians of the Three, especially Elrond.
In the Council of Elrond, during a discussion between Galdor and Elrond, it's made even more explicit that an un-augmented Galadriel (or Elrond, or Círdan) quite simply does not have the power to withstand Sauron:
'What power still remains lies with us, here in Imladris, or with Cirdan at the Havens, or in Lórien. But have they the strength, have we here the strength to withstand the Enemy, the coming of Sauron at the last, when all else is overthrown?'
'I have not the strength,' said Elrond; 'neither have they.'
So Galadriel's display of power in this scene in the movie must be ranked as a movie invention that can't be otherwise explained. You're correct: Saruman should be more powerful (Gandalf says elsewhere in The Council of Elrond that "It was by the devices of Saruman that we drove him from Dol Guldur"), and so should Radagast and Gandalf.
That's not to say that she's weak, however; for a more in-depth analysis of Galadriel's powers, see this question: What powers does Galadriel have?
Sub-answer: there's a lot more displays of magic via flashing lights/etc in the books than is commonly supposed. Gandalf hurling lightning bolts at the Nazgul on Weathertop ("such light and flame cannot have been seen on Weathertop since the war-beacons of old"), his display of power during the Warg attack ("High in the air he tossed the blazing brand. It flared with a sudden white radiance like lightning; and his voice rolled like thunder"), more lightning bolts when he rescues Faramir ("One wheeled towards him; but it seemed to Pippin that he raised his hand, and from it a shaft of white light stabbed upwards"), for example.