iTunes requires QuickTime because QuickTime is its playback engine. This is invisible in Mac OS X, because QuickTime is built-in to the system, but in Windows, it's a necessary addition. All of the audio & video iTunes plays is decoded via QuickTime’s engine.

And QuickTime’s hardly dead, seeing as it, or a variant of it, handles ALL of the playback on your iPhone/iPod Touch/iPad (since iPhone OS is based on OS X).

You can do that already. AAC is a standard; the only tracks you wouldn't be able to convert (easily) would be old-school iTunes purchases that you never "upgraded" to iTunes Plus, and there are solutions to losslessly strip the DRM from those tracks.

As for music being "locked" into iTunes, that hasn't been the case for some time now.

And you really wouldn't want to convert from one lossy format to another (AAC to MP3, in this case); the quality degradation would be noticeable, even to someone who's not a trained audio professional.

I suppose it depends on if she actually knew it's her son, but the end result is still pretty spectacularly awful.