。
She's a wonderful woman.
Literal
She [topic-は] wonderful woman is.
A model 'X is Y' sentence. すばらしい ('wonderful, splendid, magnificent') is an i-adjective covering admiration and praise; one of the strongest positive evaluators in everyday Japanese. 女性 (じょせい) is the neutral, slightly formal word for 'woman / female adult' — preferred in writing or when referring to women respectfully, as opposed to 女 (おんな), which is neutral but sometimes blunt. The plain copula だ keeps it casual.