Very good video! Awesome!
Btw, regarding HD material. Youtube have higher bitrates on that stuff. If you upscale a 360p video to 1080p and then upload it on Youtube the 1080p version will look better than 360 or 480p in the Youtube player even if the original material was 360p. Youtube unfortunately use heavier compression on the lower resolution modes. This all ofc depends on the source material. If it's lossless material in 480p than you'll see bigger difference using this method.
As an example I uploaded for myself earlier, take a look at this Tomb Raider video that was captured lossless at 320x200. It got HEAVY pixelation which causes lot of constant movement in the picture. This results in havoc for the compression algorithms. Take a look how big the quality difference is between Original, 720p, and 360p. Original is not "original" lossless quality, but a step above 1080p in resolution. http://www.youtube.com/watch?v=2LEb9WDDZtA
Your friend, you say she probably would be happy to do voice overs in other Youtube videos. Looking at her page it seems she does it professionally?