As it were

Same meaning as so to speak/in a manner of speaking.

http://learnersdictionary.com/definition/as

For Pete's sake, I've already searched for definitions people could easily find with Google in ten seconds flat. I tried to replace "as it were" for such definitions but it didn't make sense. What I want to really know is... What kind of feelings or implication does "as it were" add to "I'm in the zone"?

As it were is used to qualify a statement to indicate that it is intended to convey a general idea, but should not be assumed to be literally and precisely accurate in every detail.
"I am a teacher, as it were, on EnglishForward" would indicate I am like a teacher, or I perform some of the functions of a teacher, on EnglishForward, so for the purposes of understanding m

Then she thinks that her saying of "I'm in the zone" isn't literally accurate in every detail, and I can't understand how the expression isn't accurate. It's definitely the matter of the storyline. If you don't mind, could you check on the movie and transcript, and tell me how I should interpret the line?

In the zone is typically used in reference to sports, indicating a state of perfect concentration which enables one to perform at one's very best. She is not actually in such a state, she is using the phrase to suggest that she is concentrating hard on her own perfection, and doesn't wish to be distracted.

PonyFanFor Pete's sake, I've already searched for definitions people could easily find with Google in ten seconds flat.

You may not find the first answer you receive exactly fits your requirements, but somebody made the effort to attempt to help you. Please try to be a little more gracious in your response.