Which spelling is correct in the context: "She was a ____________ worker."?

The correct spelling is "conscientious." This word means being diligent and careful in one's work or duties, reflecting a strong sense of responsibility and commitment to quality. It is often used to describe someone who takes their responsibilities seriously and strives to do their best in any task.

The other spellings presented are incorrect variations that do not conform to the standard spelling of the word. These variations may stem from common phonetic misinterpretations of the term but ultimately do not convey the intended meaning accurately. Thus, "conscientious" stands out as the only properly spelled and recognized form within this context.