女大十八变越变越好看Slow Chinese Stories | Chinese Listening Practice HSK 3 

她已经好几年没有回家了 This is an unusual grammatical structure which takes getting used to. When an action has not occurred for a certain period of time, the time-duration appears before the verb. And a sentence-final 了 is indeed used, even though the action is negated. … 她已经回家好几年了 Normally, the time-duration appears after the verb. The sentence-final 了 indicates that the action will continue. … 她没有回家 Normally, if the action is negated, a sentence-final 了 is not used.