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She wasn't in the mood to eat lunch.
Literal
She [topic-は] lunch [object-を] eat [such-ような] mood was-not.
~ような気分ではなかった ('wasn't in the mood/feeling to do X') uses ような to create a comparison: 'a feeling like eating' → she didn't have that kind of feeling. 気分 ('mood/feeling') is the word for one's current emotional or physical state. A natural way to express disinterest in an activity.