。
She married a wealthy merchant.
Literal
She [topic-は] wealthy [genitive-の] merchant [with-と] married.
商人 ('merchant, trader') is somewhat archaic in modern Japanese — it evokes a traditional shopkeeper or trader from an earlier era. Modern equivalents would be ビジネスマン ('businessman') or 商売人 ('businessperson, trader'); 商人 is the word you'd see in historical fiction or period dramas (時代劇), or in the fixed phrase 商人の町 ('merchant town,' as historical Osaka was known). The register tilts the whole sentence slightly retro.