。
She got married in her teens.
Literal
She [topic-は] teens [in-で] married.
十代 (じゅうだい) means 'teens' — the 代 suffix marks an age range (二十代 = twenties, 三十代 = thirties). 結婚した uses the simple past. The で particle marks the time period as the circumstance or context in which the marriage occurred. Marrying in one's teens is less common in modern Japan, where the average marriage age has been steadily rising.