In our collective consciousness, saturated as it is by exposure to the 1939 movie, Glinda and the Wicked Witch are polar opposites – one is "good," the other is "wicked." But in Wicked, things aren't so black and white. So how is pink and poufy Glinda complicated here? Well, a lot of it has to do with identity crises and changes.
Though Elphaba picks up a lot of different names and identities in the book, it's really Glinda (formerly Galinda) who embodies themes of name and identity shifts. Galinda undergoes a major character shift when she becomes Glinda, but in a lot of ways the grown-up Glinda has changed back into her older self. Through Glinda we see not only how people change over time, but also how identity is fluid. So who exactly is Glinda? Let's find out.
When we first meet Galinda, she's spoiled, superficial, and more than a little naïve:
She reasoned that because she was beautiful she was significant, though what she signified, and to whom, was not clear to her yet. (184.108.40.206)
But at Shiz she's forced to confront the fact that she's led a very sheltered life and may now be in a little over her head. What's interesting is Galinda's reaction to this revelation. Instead of trying to learn more about her new environment, she seems to just dig her heels in deeper.
If she was superficial, flighty, and spoiled before, she goes for broke now. Her new friends are catty, and Galinda herself is downright mean to Elphaba at times:
[Galinda:] "And, girls, when she tried on my hat, I could've died. She looked like somebody's maiden aunt come up out of the grave. I mean as frumpy as a Cow." (220.127.116.11)
But Galinda shows some signs of depth. She isn't stupid, as some of her conversations with Elphaba reveal. She also shows hints of being capable of craftiness and manipulation. She did fabricate an entire medical condition for her Ama Clutch and then boldly sold the lie to Madame Morrible in order to keep out of the dreaded "Pink Dormitory," since living there is apparently social suicide (2.1.1).
This type of behavior might not be praiseworthy, but it does demonstrate a level of intelligence that we probably wouldn't expect from hearing the topic of Galinda's admissions essay: "The Moral Philosophy of Springtime" (18.104.22.168). Then again, writing such a thing in the first place shows a strong degree of calculation and shrewdness – it got her admitted to Shiz.
Basically, Galinda has a lot of components that can be arranged in different ways in the future. Her adult identity is really up in the air, which contrasts with Elphaba, who, in a lot of ways, seems very rooted in herself even at a young age.
Glinda emerges on the scene in very dark circumstances. Her "birth" is essentially the direct result of Doctor Dillamond's death:
Glinda – for out of some belated apology for her initial rudeness to the martyred Goat, she now called herself as he had once called her – Glinda seemed to be stricken dumb before the fact of Ama Clutch. (22.214.171.124)
The name "Glinda" is ostensibly a tribute to the slain Doctor Dillamond, but the name change is really more a result of Galinda's guilt. She felt she needed an external change to reflect the huge changes she has undergone internally. But perhaps this shift may also be a method of self-preservation, a way to keep certain parts of Galinda unchanged and allowing Glinda to assume the changed aspects. Trippy.
Glinda has a different sort of relationship with Elphaba than Galinda did. She loves her, even if she is frustrated and confused by her at times. The two women develop a genuine friendship, and the height of that friendship is their journey to Emerald City:
Glinda would start as if from a frightful dream, and nestle in nearer to Elphaba, who seemed at night never to sleep. Daytimes, the long hours spent in poorly sprung carriages, Elphaba would nod off against Glinda's shoulder. (126.96.36.199)
Elphaba taught Glinda a lot during their time at Shiz, but it's arguably Elphaba's departure that has the biggest impact on her.
Glinda spends the bulk of her life apart from Elphaba, but it's clear that Elphaba has had a huge impact on her life. When they reunite it's almost as if they haven't been apart for fifteen or so years. Their shared experiences were so pivotal that it doesn't matter that they actually spent relatively little time together. But what's really fascinating about the reunion is how Glinda's speaking style and attitude sometimes resemble Galinda's when we first met her. Glinda now seems like a blend of the superficial Galinda and the more savvy Glinda:
"Oh, yes" said Glinda in a false calm, surveying the Witch up and down, "and they would make the perfect accessory for that glass-of-fashion outfit you have on. Come on, Elphie, since when have you cared about shoes, of all things? Look at those army boots you have on!" (5.3.88)
But beneath that concern for "fashion," Glinda is also aware of what the stakes are with the shoes:
But you have to see, Elphie, the shoes couldn't stay here. The ignorant pagan Munchkinlanders ...they had put too much credit in those silly shoes.... I had to get them out of Munchkinland. (5.3.96)
Glinda has come into herself, as it were: she's a powerful sorceress, she knows how to play politics, and she can be downright devious (as we see with her interactions with Dorothy). But, as Elphaba points out, Glinda is still a superficial snob. It's notable that Glinda has retained her love of architecture and fashion, which points to her superficial nature and her tendency give too much credit to appearances.
In a way, Glinda the Good Witch is the culmination of all of Galinda and Glinda's different parts, both good and bad. In this respect she's a lot like Elphaba. The two women may appear to be polar opposites, but Boq notes some striking similarities between them:
Glinda used her glitter beads, and you used your exotic looks and background, but weren't you just doing the same thing, trying to maximize what you had in order to get what you wanted? (5.5.20)
Both Glinda and Elphaba are strong women who use all the tools at their disposal (or try to at least). And both women have changed over the years and are now made up of composite parts of their pasts. It's definitely worth noting that they are both the namesakes of legendary saints: Saint Glinda and Saint Aelphaba. These ties to legend suggest that Yackle's prophecy about two influential sisters may not have been exactly accurate. Glinda too plays a vital role in the history of Oz and notably assumed the role of the "second sister" for years:
I stood by [Nessa] when you abandoned her in Shiz.... I became her surrogate sister. And as an old friend I gave her the power to stand upright by herself through those shoes." (5.3.90)
In the end, there isn't that much of a distinction between our "good" witch and our "wicked" witch, and Glinda's major role in the novel may be to demonstrate that fact.