Answer:
It was a beginner's mistake, and Jilly had been so embarrassed for making it.
Step-by-step explanation:
This is the statement that best describes how Jilly feels about her job. In this line, we learn that Jilly made a mistake at work. She claims that this was a beginner's mistake, and that she is really embarrassed about it. From this, we can conclude that Jilly does not consider herself a beginner. Moreover, it seems like Jilly feels upset when she makes mistakes at work.