。
She felt like going for a walk.
Literal
She [topic-は] take-a-walk want-to feeling was.
~たい気分 ('in the mood to X') uses the desiderative ~たい prenominally before 気分 ('mood, feeling'). Slightly softer and more atmospheric than the bare ~たい. The structure: [verb-tai] + 気分 + だ. Other useful 気分 patterns: いい気分 ('good mood'), 嫌な気分 ('bad mood'), 気分転換 ('mood change, refreshment'). The past だった captures a momentary feeling that's now passed.