。
Yumi's happy, isn't she.
Literal
Yumi [topic-は] happy be-[polite-です]-[sentence-final-ね].
The sentence-final ね ('isn't she?', 'right?') invites the listener's agreement or confirmation. 幸せ ('happy, fortunate') is a な-adjective, predicated with です. A gentle observation that pulls the listener into agreement.