。
She is already married.
Literal
[topic-は] already already married-is.
もう既に layers two 'already' adverbs — もう (everyday) plus 既に (more formal/literary 'already, previously'). This isn't a mistake: the redundancy intensifies emphasis, similar to English 'already' + 'long ago.' The combo is common when the speaker wants to underline how settled or past-the-point-of-discussion the situation is. 結婚しています is the resulting state of 結婚する ('to get married') — Japanese describes 'being married' as the persistent state following the punctual marriage event, not as an inherent property. Without the ~ている, 結婚します shifts to a future or general 'will get married / does the act of marrying.'