The sentence states: "The event planner did not see planning parties as the $\qquad$ of her job; those occasions were merely one component of her work, which included client and vendor relations as well."
- The crucial part is "merely one component of her work." This implies that party planning was not the whole, or the most important part, of her job.
- The blank needs a word that means the "entirety" or the "most important part" or "main focus" of something, because the second part of the sentence contrasts this with it being "merely one component."

Let's look at the options:
- A. highlight: The most interesting or important part. If she didn't see it as the highlight, it fits the idea that it was just one part, but "sum" or "totality" fits the "one component" contrast more directly.
- B. disadvantage: An unfavorable circumstance or condition. This doesn't fit the context of describing a component's scope.
- C. sum: The whole amount; the totality. If she didn't see it as the "sum" of her job, it perfectly matches the idea that it was only "one component."
- D. irony: A state of affairs or an event that seems deliberately contrary to what one expects and is often amusing as a result. This is irrelevant to the scope of her job.
- E. totality: The whole of something. Similar to "sum," if she didn't see it as the "totality" of her job, it directly contrasts with it being "merely one component."
- F. incentive: A thing that motivates or encourages one to do something. This doesn't fit the context of describing the scope of her job.

Conclusion:

The words that best fit the blank are those that mean the whole or entirety of her job, in contrast to just being "one component." "Sum" and "totality" are perfect matches. "Highlight" is plausible, but "sum" and "totality" are more direct antonyms to "one component" in terms of scope.

The correct answers are C. sum and E. totality.