。
She lowered the blinds.
Literal
She [topic-は] blinds [object-を] lowered.
降ろす ('to lower, take down, let down') is the transitive partner of 降りる ('to descend'). It's used productively for lowering things into position — blinds, flags, prices, ranks. ブラインド is a katakana loanword for window blinds, distinct from ブラインドネス or other senses of 'blind.' The plain past 降ろした reports a simple completed action.