On the flip side of that coin, though, Emily had already seen that Lorelai herself had not "gotten over" Christopher even in the decade and a half they had not been together. Anybody with half a brain could pick up on that in Christopher Returns, Presenting Lorelai Gilmore, I Can't Get Started, Haunted Leg, and others. Emily overstepped her bounds, absolutely, but I really do believe she thought Lorelai would have been happy if she and Chris were finally able to make a relationship work. WE knew that Luke was the one Lorelai was really supposed to be with, sure, but keep in mind Emily had already seen Lorelai break off one engagement to a man she was supposedly serious about and moved on to Christopher just a few months after that.
I can see why Emily refused to let go of the idea that Christopher was "the one" until he and Lorelai actually got married and divorced, that's all I'm saying.