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She pretended she couldn't hear what he said.
Literal
She [topic-は] his [genitive-の] said thing [subject-が] not-audible [like-ような] pretense [object-を] did.
An expanded version of the ふりをする pattern — adding ~ような (with ような 'like, as if') to give 'pretend as if X.' 言った事 ('the thing he said') is a relative clause + nominalizing 事 (こと/事 used interchangeably). The whole structure: '(she) did the pretense of being like (it's the case that) his words were not audible.' A longer-winded way of saying she pretended not to hear.