。
She married him last year.
Literal
She [topic-は] last-year him [with-と] married.
結婚する ('to marry') always takes と for the partner, never を — the marriage is a joint event, not something done *to* someone. So 彼と結婚する rather than 彼を結婚する. The same pattern shows up with verbs of mutual action: 話す ('talk with'), 喧嘩する ('fight with'), 別れる ('part with'). 去年, the everyday word for 'last year,' floats freely as a time adverb without needing a particle (compared to 来週, which often takes に in formal contexts). In Japanese, women traditionally adopt the husband's family name on marriage; this is a famously contested topic — Japan is the only G7 country still requiring spouses to share a single surname by law.