。
She's out at the moment.
Literal
She [topic-は] now out-on-an-outing-during is.
外出中 ('during outing') is a clean, set form for 'out, away from where the speaker is,' useful for phone messages, office signs, or status updates. The suffix ~中 (ちゅう) attaches productively to verbal nouns to mark 'during X': 食事中, 会議中, 入浴中, 通話中. Compare 外出中 with 留守 — 留守 means 'absent (especially from home)' and is often paired with 番 in 留守番 ('house-sitter'). For someone briefly out of the office, 外出中 is the standard.