。
She fumbled around for the light switch in the dark.
Literal
She [topic-は] dim-place [in-で] light [of-の] switch [object-を] hand-feeling [with-で] searched.
Two で in one sentence with different functions: 暗がりで marks the location of the action ('in the dim space'), and 手探りで marks the manner/means ('by groping, by feel'). 手探り ('hand-feeling') is a compound noun describing fumbling without sight. 明かりのスイッチ uses the loanword スイッチ (English 'switch'); 明かり ('light') is the native equivalent of 電気 ('electricity, lights'), often poetically chosen to evoke a single source of light against darkness. 捜す uses the kanji for 'search for someone/something missing,' distinct from 探す ('look for what one wants').