。
She pours her energy into parties.
Literal
She [topic-は] parties [into-に] energy [object-を] uses.
精力を使う ('use energy / vigour') is a stock verb-object collocation; 精力 (せいりょく) is a slightly elevated word for energy, vitality, or vigour, distinct from the everyday 元気 ('cheer, pep') or エネルギー (the loanword for physical/scientific energy). The non-past 使う here gives the sentence a habitual or characterizing reading — she's the kind of person who throws herself into parties — rather than describing one specific occasion. に marks the target / arena into which the energy is directed.