She attempted the tightrope without a safety net.

Literal

She [topic-は] net [object-を] not-stretching tightrope [to-に] challenged.

綱渡りに挑んだ (つなわたりにいどんだ) — 綱渡り ('tightrope walking') and 挑む (いどむ, 'to challenge/attempt') convey daring. 網を張らないで ('without stretching a net') marks the dangerous condition.