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She married a wealthy old man.
Literal
She [topic-は] wealthy [genitive-の] old-man [with-と] married.
Stacking attributes via の: 金持ちの老人 = 'wealthy old man,' with each noun modifying the next through の. 金持ち ('rich person') is built compactly: 金 (money) + 持ち (one who holds) — 'one who holds money.' The same productive ~持ち suffix appears elsewhere: 力持ち (strong person), 顔持ち (countenance), 受け持ち (one in charge). The sentence has a faintly editorial tilt — pairing wealth with old age in a marriage context invites readers to fill in their own assumptions about the dynamic.