DR Druxy, both of my grandmothers collected antique glass as does my mother. She's taught me a lot about it. I am also very familiar with sad feelings when a family piece is accidentially broken, including times when I was the culprit and not the cat. There are many pieces that can't be replaced or repaired but with a lamp, you can often find a replacement for the shade. It will still be a family lamp, it's just had an extreme makeover!
I hope your wife finds her shade on the sites I sent. If not, there are lots of sites out there. I've gotten dishes from discontinued sets through Replacements.com, but I think they just do dishes. Good luck!