。
She froze in fear at the sight of a huge spider.
Literal
She [topic-は] big spider [object-を] saw-and body [subject-が] froze.
身がすくむ ('to freeze, be paralyzed with fear') is a set idiom literally 'the body shrinks / cowers.' すくむ (a kana-favored verb) means 'to freeze in place from fear, surprise, or shock.' 身 ('body, oneself') is a slightly more poetic / archaic word for the body than 体 — used in many idioms (身につける 'master,' 身を引く 'step back'). The te-form 見て here links cause and reaction — 'seeing the spider, [she] froze.'