Ok, I know it is slang, I'm pretty sure it's derived from the French 'chère' that I think roughly translates into English as 'dear'. Judging from Caroline's accent (I'm an Aussie so I could be very wrong here, please let me know :D) I think she's from New Orleans, which has heavy french influences, including its language. So I always assumed it was a N'Orleans slang term.

mmm im doubting the spellin "Sheri" cos when you look it up in the scripts it says "Chérie". and agree its from French and it means "Darling", "Dear"...but i would say in more sarcastic way...