、。
Jane turned pale when she saw the cooked snails.
Literal
Cooked snails [object-を] seeing, Jane [topic-は] turned-pale.
料理された is the passive form used as a past-tense modifier meaning 'cooked/prepared.' カタツムリ (snail) is written in katakana as is common for animal names. 青ざめる literally means 'to become blue-pale' — Japanese uses 青い for the pallor of shock. The て-form (見て) connects two sequential actions: seeing, then turning pale.