Here's what I think about the four girls themselves.
The show worked out that there were
2 Extraverts/2 Introverts (Carrie & Samantha/Miranda & Charlotte)
2 Sensors/2 iNtuitives (Charlotte & Samantha/Carrie & Miranda)
2 Thinkers/2 Feelers (Miranda & Samantha/ Carrie & Charlotte)
2 Judgers/ 2 Perceivers (Miranda & Charlotte/ Carrie & Samantha)
Obviously they didn't do this deliberately, lol.. just found it interesting as I was typing them.
Makes sense to me.