It really hit me during this rewatch how completely touched/floored Glinda was by a genuine act of kindness/goodness. Up until that point, she only did “good” things for her own personal gain, that were really kind of mean, underneath. And then Elphaba turns around and insists she join Madame Morrible’s seminar, even though the two of them didn’t like each other at all, because she knew Glinda wanted it more than anything.
Before this, she didn’t allow herself to see who Elphaba was, probably because nobody else did, and Glinda so wanted to be praised/liked by everyone around her.
You can see the realization on her face so clearly, though, as she watched Elphaba dance alone among all the ridicule😭
Glinda the Good learned to be that way, at least in the end, because the so called Wicked Witch showed her what the word really meant.