Galinda really was hanging around the "wrong crowd" when we first met her. Her catty, snotty, superficial friends fueled those unfortunate qualities in her. They all seemed to have a sort of symbiotic relationship, feeding off of one another's bad behavior.
These highly interchangeable girls only show very brief flickers of personality and individuality. The one who breaks out as the most individual character is Milla, who marries Boq. During the early days of their marriage, Milla constantly threatens to kill herself because she hates Munchkinland so much (3.2.4). Boq and Milla's overwrought romance doesn't go the Revolutionary Road route, though. Instead, these two mellow out considerably and end up more like the Weasleys, complete with a passel of kids.
Pfannee and Shenshen are the snottier of Glinda's friends. We never quite forgive Pfannee for tricking Elphaba into crashing their summer vacation. Shenshen doesn't stand out all that much, though she is, along with Avaric, the only one who isn't squeamish at the Philosophy Club (126.96.36.199). Presumably one of these girls married Avaric, but he jokingly never says who. In a way, Avaric's dig about "who can remember" (5.7.45) is a reflection on the cookie-cutter similarities between Pfannee and Shenshen.