She nailed the show this time on Letterman, there's no doubt about that. It was brave move to come back up again after SNL performance. 
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I really don't think its all up to Lana, if she wants to postpone the shows or not. When you sign a contract with major record label, you basically are their product all the way. So if they say "it would hurt record sales", you can't do much about it by your own. 
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