It's possible you're thinking of the cursed necklace she received from an anonymous sender, which turned out to be a Horcrux. This incident left Katie poisoned and in a coma for a period of time.
However, the Horcrux itself is not technically a curse, but rather a magical object with powerful dark magic woven into its existence. It's important to note that Katie was not directly cursed by someone, but rather affected by the object itself.