@XTinkerBellx said it right. Kelly didn't die or was killed or something like that, she was replaced by Chelsea.

I wish they would bring Kelly back

Chelsea didn't replace Kelly, Chelsea IS Kelly.

https://static.wikia.nocookie.net/barbie/images/2/2f/IMG_6932.JPG

@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.

@Vernorexia Do you mean in the translations of the shows and movies? I mean, sometimes (quite rarely) I watch Barbie in Hindi, but they call her Chelsea.

@Barbra Millicent No, not Hindi, just British English and Europe. Kelly Club was called Shelley Club, as seen on this UK computer game. This was in the early 2000s when Kelly was called Shelley, you weren't even alive

In the cartoon "Kelly's Dream Club" She had a friend named Chelsie, spelled differently from Chelsie. She is the redhead, and not related to Barbie.

There really wasn't a reason Kelly/Shelley became Chelsea, because she had never been called that before. My best theory is Chelsea is Kelly's middle name and for some reason she chose to go by that name.

https://community.creations.mattel.com/forums/topic/66350-name-change-for-kelly/?ct=1654548198

In 2010, a Barbie collector said, "We were told at convention in the BFC* event that Kelly's name will indeed be changed to Chelsea. Kelly has been known as Shelly in Europe because of licensing/trademarks and a consistent name worldwide was preferred. We were told that Chelsea was originally Kelly's middle name and was chosen for the continuation of the revamped and updated upcoming line."

*BFC means Barbie Fan Club.

That matches what the text says in the pic @The Beautiful People posted where Chelsea says her name changed so she could be universally known by one name.

I think it was just done as a joke aimed at people who knew Chelsea as Kelly.