。
She just stepped out a moment ago.
Literal
She [topic-は] just-now stepped-out.
今し方 (いましがた) is a literary, slightly old-fashioned word for 'just now, a moment ago' — equivalent to plain 今しがた or the more colloquial さっき. The し is an old emphatic particle preserved in this fossilized form. You'll hear it in formal speech, customer service, or in writing aimed at an elevated register. The polite past 外出しました fits with the slightly elevated tone of 今し方.