。
She shuddered at the thought of snakes.
Literal
She [topic-は] snakes' matter [object-を] thinking-about shuddered.
のことを思う ('to think about, consider') is a stock pattern for thinking about someone or something; ~のこと softens the reference and signals 'the matter of, regarding.' 身ぶるい ('shudder, shiver of revulsion') is a noun ('body-shake') that becomes a verb with する; here it appears in past plain form 身ぶるいした. The combined image is vivid and physical — just imagining the snakes is enough to make her body involuntarily shake.