。
She caught sight of a bear and froze.
Literal
She [topic-は] bear [object-を] caught-sight-of, body [subject-が] cringed/froze.
Two evocative pieces of vocabulary. 見かける is a compound verb (見る + かける) meaning 'to catch sight of, to happen to see' — distinct from the deliberate 見る ('look at') by implying an incidental, glimpsed encounter. 身がすくむ literally means 'one's body cringes/shrinks' — used for the involuntary tightening of the body in fear, the freeze response English would call 'frozen with fear.' The body part 身 here is grammatically the subject (marked が), with the cringing happening to it. This kind of body-part-as-subject construction is common in Japanese for involuntary physical reactions to emotion.