No, not at all. The Canon digital camera use the EOS system which was introduced for auto-focus film cameras.
I'll bet it's that switch in lens mounts that got her mad enough at Canon to drop them and go with Nikon. Back when all the companies were switching over to autofocus only Nikon did not change mounts. So Long time Nikon users did not have all their lens become obsolete with the switch. I'm sure Canon learned something and now the EOS lens work with digital they are not so dumb as to loose their customer base again.
On the other hand my 1970's vintage Nikon Lenses mount on my new Nikon DSLR. and the new Nikon optics mount on my 70's vintage film body with some exceptions
But do NOT discount film and manual focus. Let's say you go on a long backpacking trip. How would you re-charge the 20D battery? and film still has better quality then most DSLR cameras. My old camera will still work even with no battery installed. If she has an old Canon and a set of good Canon Prime lenses then you can actually do better quality work with then than with the 20D but you have to wait to process the film and (likely) scan it to digital files.