。
She replied that she had never met that man.
Literal
She [topic-は] that man [recipient-に] met [past-experience-こと-が] not-exist [quotative-と] reply [object-を] did.
返事をする is the more conversational way to say 'to reply,' constructed as 返事 ('reply' noun) + を + する — a light-verb construction where the noun does the semantic work. It contrasts with 答える, which is more direct and often used for answering specific questions. The full quoted clause is held together by quotative と, and ~に会ったことがある covers any meeting in life-experience terms — 'I have/haven't met X in my life,' distinct from a single recent encounter.