[Pitchwife]

The funny thing is (as I'm sure you all know), the character of Galadriel (including the poems attributed to her) first emerged during the writing of LotR, and she was only written into the Legends of the First Age after LotR had been completed.
Considering that, I think it highly unlikely that the Professor had any precise idea of who she was, what she had done previously and whether there was a Ban on her or not when he wrote the Lothlórien chapters. (Although, once he had invented her, his mind probably worked like mad trying to determine where she came from and trying out possible back-histories for her.)
For all we know, he wrote her songs (especially 'I sang of leaves...', which I actually prefer to 'Namarie') just because they felt right at the time and only afterwards went into constructing various and mutually contradicting historical explanations for what his Muse had dictated.

As for Galadriel's temptation scene: 'going into the West' was the common fate of all Elves in the Third Age; that was rather trivial, even Ted Sandyman knew about it (cf the conversation at the Green Dragon, The Shadow of the Past). OK, Galadriel, being enamoured of Middle Earth, tried to resist it; and surely the Ring offered her the ultimate chance of doing so, giving her the unique chance to order M-E according to her own liking. Rejecting the temptation, she simply accepted the fact that her own fate would be just like that of the rest of her people: "I will diminish, and go into the West, and remain Galadriel", instead of becoming a Dark Queen. None of this seems to call for a special Ban on her being lifted or not to explain her words and actions.