。
She fainted at the sight of blood.
Literal
She [topic-は] blood [object-を] saw fainted.
卒倒する is a punchier, more dramatic word for 'to faint' than the everyday 気を失う ('lose consciousness'). It carries a slight literary or theatrical flavor, the kind of verb a narrator might reach for when a character collapses suddenly. The phrase 血を見て卒倒する ('faint at the sight of blood') is a recognizable trope, since the blood-phobic faint is its own minor genre in Japanese fiction.