My theory is that Chelsea's real name is Kelly. Then in her kindergarten class she decided to go by her middle name, Chelsea, because there was another Kelly in the class. This theory was inspired by the two Kelly's situation on The Office lol https://youtu.be/8X1h0zfIkck
@The Beautiful People Yes, it does make sense that Chelsea is just an older Kelly. But what is strange about that is she was never called Chelsea in other countries. She was called Shelley.