。
She's about to leave.
Literal
She [topic-は] depart [about to-ようとしている].
~ようとしている captures the moment just before an action begins — she's on the verge of departing. This differs from ~ようとする, which can mean either 'try to' or 'be about to' depending on context; the ~ている form strongly signals the 'about to' reading, freezing the moment of imminent action.