I'm assuming your target media is a VIDEO DVD - ie: one that will play on a generic standalone DVD player
No matter how you slice it, you're going to loose *some* quality (how much will depend on your encoding methods what prepping the files for DVD and how long your materials are which will directly affect how much you can store on a DVD depending on your selected bitrate - some quality loss will not be detectable to people especially since they will have never seen your master footage) - specifically if your making a video DVD, since that quicktime video of yours will be converted into a mpeg2 stream (as would her avi file) to be able to be used by a DVD authoring program - and this is what I'm assuming you want to do - to be able to play it back on a standard DVD player.
Plus, I don't know what your master resolution is - ie: HD/720p/1080i/p or SD - but if it is HD, you'll loose resolution when you put it on a standard video dvd (since a video dvd is SD). If the video is HD, you could make an AVCHD DVD, but that would require an authoring tool that would support that (ie: Adobe Encore I think does, Roxio Toast Titanium 10 w/ bluray plugin, etc.), and you would only be able to fit a short length of video on the disc depending on compression and DVD size (ie: single layer or dual layer dvd) - plus they would need a bluray player at where you're going to have your video on display at to be able to play back an AVCHD DVD.
In terms of converting for your DVD, assuming you have Final Cut Studio, you'll need to use Compressor to convert your footage into an mpeg2 stream w/ ac3 audio - I'd suggest converting a small section with the most amount of movement to look at and compare to your master footage to find an ideal bit rate - don't compare compressed footage to compressed footage (ie: subsequent runs of compressor) - always compare your output of compressor to your master file to determine the quality compared to your original.
In terms of her footage - I've honestly never tried using compressor to convert an AVI file and am not sure if it will do it or not. If not, you could always use ffmpegx to try to convert the AVI into an mpeg2 stream w/ ac3 audio.
You could also get her to convert the footage to mpeg2 stream w/ ac3 audio - I haven't used Premiere in a long time, but if it doesn't have an export directly from Premiere itself that offers mpeg2 stream/ac3 audio, she should be able to take the footage into Encore and convert it there and send you the converted video. I'd imagine that DVD Studio Pro would accept an mpeg2 w/ ac3 audio encode from Adobe (I assume you're using DVD Studio Pro to author your video dvd)
Just some thoughts on the matter.