Maybe she does want to hear it, as it wasn't on the list of things she doesn't care for. Neither was snoring.
Seriously, though, building a temporary wall can certainly be done, but keep in mind that it will be heavy and bulky to put into position on top of the existing wall if framed with conventional 2 x 4 stock. Building it in shorter sections than the total length needed, about 4' long each, would make them more manageable. A much lighter configuration could be made using a single frame of just 2 x 2s, with a layer of 1-1/2" rigid foam glued to each exterior face (textured/painted to suit). The foam would also cut down on noise transmission.