Looks to be a simple matte effect. IMO, they shot her on a green screen, put the wall background behind her in one pass. Then use duplicate the keyed green screen footage and use that as a track matte. That means that what you place below it(CU of her singing) will only show in the green screen body shot. Finally the opacity of the CU shot was lowered a bit.
There's a couple of links to track mattes and tutorial about them in This THREAD
Johnny Cuevas, Editor
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