。
She danced so gracefully that she surprised us all.
Literal
She [topic-は] us all [object-を] surprise [extent-ほど] gracefully danced.
~ほど ('to the extent of') here marks a result extreme enough to produce surprise — 'danced gracefully to the degree that she surprised everyone.' The pattern [clause]ほど + main predicate is the classic way to express 'so much that...' / 'to the point of....' 優美 ('graceful, elegant') is a slightly literary na-adjective — paired with the adverbial に form 優美に modifying 踊る. The whole sentence has a written, almost novelistic feel.