What a tantalizing notion that LuPone could have improved in the new production! Although weren't most of the changes not related to the core Norma material, aside from whatever adjustments were made for Close's vocal abilities? Like, does the addition of Every Movie's a Circus (a horrible song in my opinion) for the ensemble make the show better and improve the Norma experience?
I think you have to take LuPone's animosity with a grain of salt. It's not rational, but her thinking was no doubt clouded by the anger and sadness she felt being from being fired. You'll notice if you read her book that she holds (or held) a lot of grudges. And this it the theatre and people are dramatic. I suppose there is a world in which LuPone could have been terribly rational and said: well of course Glenn Close was just taking a job she was offered, I can see beyond my own situation and acknowledge that. But that would have been awfully clear headed. Maybe unrealistically so.