。
She's happy.
Literal
She [topic-は] happy is.
The simplest possible polite assertion: a topic, an adjectival predicate, and the polite copula です. 幸せ behaves like a na-adjective here — taking です directly without an intervening な (which is for noun-modifying use only). Same pattern with 元気です, 静かです, 親切です. As a baseline frame, this is what every learner builds up from.