。
She felt like giving up on the plan.
Literal
She [topic-は] that plan [object-を] want-to-give-up feeling did.
~たい気がする is a slightly hedged variant of plain ~たい — instead of bald 'I want to', it softens to 'I have a feeling I want to'. The feeling is presented as a fleeting impulse rather than a settled desire, which suits an internal moment of wavering. Notice how Japanese stacks layers of indirection here: あきらめる ('give up') becomes あきらめたい ('want to give up'), then ~気がする adds 'feel like', and the whole thing reports as 気がした in plain past — a chain of nuance English would compress into one or two words.