Wicked is a frame story. This often gets lost in the stuff that happens inside the frame. But it's wildly important who's doing the framing - Glinda - and why - because she's grieving.
But! It's not just grief! It's a decision. It's a character point! It's very much akin to the moment where a young Galinda stepped onto the floor of the Ozdust and started to dance opposite a young Elphaba... and just as delicate a moment.
Because what we definitely don't talk about enough is that Glinda is telling this story in a way that explicitly breaks a promise she's just made to Elphaba near the end of the story. Glinda, panicked and distraught at realizing what's about to happen and her own inability to stop it, cries, "I'll tell them, I'll tell everyone the truth!"
To which Elphaba immediately says, "No. They'll only turn against you."
"I don't care!" Glinda says.
"Well, I do!" Elphaba retorts. "Promise me you won't try to clear my name."
Overcome, Glinda promises in the face of Elphaba's fervor for her safety... and then turns around and immediately breaks that promise.
The thing I also love about this is that we don't see the reprecussions of her decision. We have no idea how it goes for her - if in fact "they" turn against Glinda. Chronologically, the last we see of Glinda in the show is her hovering on the decision to tell the story. "Yes, I was her friend. Yes, I loved her. This is how it happened, and this is what it meant."
Whether or not they turn against her is irrelevant. The fact that Glinda's telling the story at all is her final triumph over her character, her absolute culmination of self. That it's also a testament to Elphaba and their friendship - ultimately the final and most important thing to her - is beautiful. Here, whatever else comes, she's found not only strength, but peace.