。
She gave me a wonderful gift.
Literal
She [topic-は] me [to-に] wonderful gift [object-を] gave.
素晴らしい is one of those reach-for-when-you-mean-it adjectives: 'wonderful, magnificent, splendid.' It carries more weight than 良い ('good') or 素敵 ('lovely'), implying genuine impressed admiration. Reserve it for things that actually warrant the praise — a less-strong adjective in its place would still be perfectly grammatical, just paler.